Show Notes

• End of the World (NOT) Cruise
• Google+: Fraser, Pamela
• Subaru Telescope
• How to Create a Flat Field — AstroWise
• IRIS software
• REGIM Software
• A list of software for Astrophotography — AstroPix
• Maxim DSLR — Michael Covington
• GIMP
• Adobe Photoshop Lightroom
• RegiStax
• FITS Image Viewer
• IRAF Software
• AIP4WIN Info and Handbook
• CCDSoft
• Maxim DL  – Oceanside Photo and Telescope
• Mira software
• IDL software
• FITS Liberator
• Cloudy Nights Forum
• Universe Today Flickr Group
• The World at Night (TWAN)
• Ice in Space
• Astronometry.net — for automatic image annotation
• Astrodatamining.net – another resource for annotating objects
• http://iraf.noao.edu/ – for filtering the sodium light and increase the contrast

Transcript: Astrophotography, Part 3: Image Processing

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Fraser: Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos, where we help you to understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University – Edwardsville. Hi, Pamela. How are you doing?

Pamela: I’m doing well. How are you doing?

Fraser: Doing good. So, we should plug again about the “End of the World” cruise. Just to let people know, we are kind of quietly plugging the “End of the World” here at AstronomyCast before we plug it in sort of wider audiences, so I haven’t mentioned it on Universe Today, and we haven’t got Phil over at Bad Astronomy to mention it and so on, mostly just…not that he necessarily would, but we’ll ask, but just cause we want to give AstronomyCast listeners sort of a more of a chance to get in. And if you do want to participate, book a room on the cruise, book a cabin and join us. So remember we’re going to celebrate the end of the world, December 21, 2012, cruising the eastern Caribbean on…you know, and even visiting Mayan ruins when it’s all supposed to end.

Pamela: So you can get all the details if you go to Astrosphere.org and we have a phone number for you to call. The travel agent who’s booking everything, her name is Zelda, and when you talk to her just tell her, “AstronomyCast sent me,” and we’ll go on our own adventure thanks to Zelda.

Fraser: Perfect. Alright, well let’s get on then. OK, time for part three of our tour through the hobby of astrophotography. You set up your gear, take some clear images, and now we’re going to help you turn that raw data into the kind of amazing photographs you see in books and on the web. So would it be safe to say that a lot of the magic of good astrophotography comes from this post-processing world? Software…?

Pamela: I’d say the vast majority of the magic comes from the post-processing.

Fraser: Yeah, yeah, that it’s really…I mean, you set up your, you’ve got good gear, you set up your camera, you press a button a bunch of times, but there’s actually so many options in the way you set up your software, and the way you set up your image, and the way you combine them and collect them and tune and remove noise and all that. That’s where it really comes together.

Pamela: Well, what’s really amazing is you can take the best images any human being on the planet has ever taken, and if you process them wrong, it will be useless junk, but you can take some kind-of-mediocre images on the sky — clouds, Moon pollution, whatever it is that affects the images, but with proper post-production, you can make those images really shine.

Fraser: Right, and so then what we’re really talking about today is, you know, you’ve taken all those pictures, you’ve got them filled up in your camera, you connect them to your computer, you download all of those raw images, and then what on Earth do you do with them to then make that final photograph? So, I think, let’s go back again and let’s talk about the different, you know, the different styles of astrophotography, the three styles that we’ve already talked about, the connecting your digital single-lens reflex camera to a tripod, taking some long…a series of long exposures in raw format, you know, and they’re going to be seen on the camera, you need to pull them off on your computer. We’ll talk about the process where you’ve got a webcam attached to your, you know, medium-range telescope, and you’re trying to go after the planetary stuff, the bright objects in the sky, then the really detailed, $20,000 camera-telescope-mount set-up, where you’re using a CCD array to pull data off as well. So let’s go back to the DSLR route. Let’s…you know, we talked about last time that we want to get these really, nice RAW images, the RAW format: R-A-W, you know, like all in capitals. What do I do with them? And I’ve…you know, what now?

Pamela: Well, so the first thing you do, no matter what, is you back-up your data, and the reason I say this is when you’re going through processing the images, it’s very, very easy to click a switch in your software such that it overwrites the original images, and if you don’t like what you did, you can’t go back and try something else if you overwrote them.

Fraser: Right, and that’s where the art comes into this is, as long as you keep that raw data separate, take a shot at it try to get an image result, and if you don’t like it, just go back to the beginning, take another path, take another crack at it, and maybe you’ll get an outcome that you’re a lot happier with.

Pamela: And this is something that even the pros do. I’ve been working with an absolutely amazing telescope driver image-reducer, basically, data miracle man out at Southwest Research Institute, and he’s trying to coax amazing images out of the Subaru Telescope, which is one of the world’s largest telescopes down in Hawaii. And he’s on his third pass through the data, each time revising the software he uses, each time changing the options that he takes to get it just a little bit better, and a little bit better, so no matter how good you are, there’s always that chance you’re going to start from the beginning.

Fraser: Now with the, sort of, that original method we’re talking about, the first of our three techniques, you know, I’ve got all these raw images of, like, wide-field, Milky Way, you know, each one was for, whatever, 10-30 seconds…what do I do with them?

Pamela: So the first thing you do is you need to do some calibrations. So here is some steps where, first things first, you can do a number of different ways to check for variations in how sensitive your camera is across the entire field. You can either take images of an evenly illuminated surface: a white wall, the twilight sky. Some people actually will create out of plexiglass these light boxes that they then attach their camera to out of focus to get this evenly illuminated image. Once you have these evenly illuminated images — these are called flat fields. The other type of thing that you want to do is measure all of the noise within your detector. So you can do this using what’s called dark images. This is where, depending on your camera, either your camera automatically every time you take a long exposure takes a second long exposure with the shutter closed, and then it subtracts off that shutter closed image because that image only contains the noise, and if the noise is consistent from one image to the next, when you subtract it off, you can just get rid of that noise. This is the same way noise-canceling headphones work, but this is the light equivalent of those noise-canceling headphones.

Fraser: And is this ability somehow provided by software like Photoshop, or is there some kind of special software that you need to use?

Pamela: Well, you can do it in Photoshop, but Photoshop’s not designed for it, so here you want to break down and either download some software – there’s a number of options out there, IRIS is a good one that runs multi-platform, there’s another one called REGIM – it has a lot of its instructions in German, so I tend to go to the IRIS site instead. A lot of that website is written in French, but the IRIS stuff itself is in English. These free software packages will help you figure out how to do all this image calibration. Now, if you’re interested in spending some money, Maxim DL has Maxim DSLR as one of its options, and this is an amateur astronomy imagery production package that has been tailored to meet the needs of everyday people trying to get the best astronomical images in the world. There’s lots of other software out there; these are the ones I find useful for working with DSLR cameras.

Fraser: And so, what do they do to your images? I mean, do they output a whole bunch of more images, which then had their light balanced out, or does it actually handle the merging as well?

Pamela: It does all of these different steps. So the first thing it will do is if your camera doesn’t automatically remove the dark current for you (which a lot of the cameras do), you feed it, you tell it what are your dark current images, and it will combine all of them and then subtract those off of your science images, your flat-field images. Then the next thing it will do is you feed it those images that I told you about of the evenly illuminated surface. So you feed it those, it adds them all together, but it does it in a way that averages everything together, so if one pixel is hot in only one image, it ignores it, but if it’s always a little bit hot, it averages those values together to get it hot, but in a typical behavior, so now you have a typical, how-your-camera’s-misbehaving image, and this it divides off so that anywhere where your camera’s a little too sensitive to light, it makes it fainter, anywhere your camera’s typically under-sensitive to light, it makes it brighter. And this flattens out your image so that the sky is evenly illuminated, if it’s actually evenly illuminated. If there’s dust, it fixes the dust. So that’s the second step.

Fraser: So is that just like a one-stop shop? In other words, you’ve got your RAW images, you feed them into one of these software packages that we talked about, IRIS or Maxim, and then out comes one of your final ones? After you’ve mucked with all the features and you tweak all the settings, and you color balance and blah, blah, blah, you know, read the instruction manual, the point being (that was the technical term, of course)… bayesian light, annotation, heurism, um, but you know, [laughing] you, you…will that just output your final picture, you know? You’ll be mucking with the features and then out will come the final image, or do you gotta do more?

Pamela: No. So you use the software like REGIM, like IRIS, like Maxim DSLR to get all of the noise that you can get removed from your images, to get all of the dust and the optical issues. You use it to fix all the stuff that’s wrong, but you still have images that aren’t art. You still often have just black and white images. To go that extra step to stretch the colors, to adjust what do you actually want red to be — here most people actually resort to Photoshop, and that’s where the big bucks are. Now, if you’re not ready to spend the money in Photoshop, a much harder to use, but also a very powerful software tool is GIMP. GIMP is the open source community’s answer to Photoshop. It has lots of powerful tools, it has fairly good documentation, it’s not as intuitive to use as Photoshop, but it’ll get the job done.

Fraser: Yeah, now Photoshop is not intuitive to use, so that’s…unfortunately, it’s about three steps below the controls of a 747, but you know, I mean, I use Pixelmator on my Mac and it’s good. It does most of the things that Photoshop does. Gimp is free if you’re willing to sort of beat your head with a hammer, and Photoshop is expensive. And someone in the Google plus hang-out is recommending Adobe Lightroom, so there’s another choice as well, but the point being that that’s where the art happens. You’ve got that final place where you then create the art. You know, I can see situations where you’ve taken this great big wide-field image, you’ve got some horizons, some trees, and then you’ve also got the night sky up above and you’re trying to make it look that you can see the you know that horizon and see the city lights, but then at the same time have the Milky Way stretched above and it all look like art, so I think that’s really cool. OK, now let’s kind of go back around to that next technique that we’ve talked about where we’ve got the little webcam, we’ve connected it to our eyepiece and we are dropping out video of Jupiter, or Saturn, or you know, of the Moon. What, uh, how does that work then?

Pamela: Here it’s actually awesomely easy thanks to a piece of software called RegiStax. Now, it’s only going to be easy if you have access to a Windows system. So all you folks like me out there who are running OSX, it’s time to install the MWare BootCamp parallels; all you people on Linux, it’s time to dual boot. Suck it up, pay the money for windows because RegiStax is free. It doesn’t balance out in the end, but RegiStax, if you’re going to be doing this sort of astro-webcam imaging — it’s designed for planets, and planets are actually much harder to cope with than stars because when you’re trying to align all of these images, if you’re looking at a star field, you grab 5, 10, 20, 30 stars – as many stars as you can, and you tell your software, “Grab those stars in every single image. Align, stretch, rotate, whatever it takes to get those images to line up perfectly.” Do not try this at home in Photoshop; you will hate yourself. Use astrophotography software to do the stacking. Now, with planets you often just have one giant, round (hopefully round), object that doesn’t have sharp features to align on. RegiStax has coded black magic in it where it’s able to figure out, based on the edges of the sphere, what needs to be done — sphere projected into a circle for your image, what needs to be done to align everything. And it’s also pretty good about helping you reject things because there’s always going to be those images where the sky misbehaved, where you walked too hard and you jiggled your telescope, and it will help you go through and do everything you need to do to get a great image out the other end.

Fraser: So this software will line up all the frames to help make sure that you’ve got everything nicely lined up, and then let you go through the frames and just kind of go, “Ah, blurry — throw it out. Oh, that’s crisp — let’s keep that one. Ooh, there’s a little bit of a better edge on the storm there — I’ll keep that one.” And then, I’m guessing, give you some way to sort of pull out certain features and push other features back a bit.

Pamela: Well, what it’s going to allow you to do is add everything together, and it’s in this adding together part that it takes the information, and anything that’s faint when you add it together is going to get brighter and brighter and brighter. Now, this isn’t going to allow you to say, “I want the red redder.” Again, you use RegiStax to do the crunching part, and then you dump the result in Photoshop or Gimp.

Fraser: Right, but you’re going to end up with one image — one great, big, you know, high-definition image that you’re then going to color balance and change the saturation and the hues and all that kind of stuff in Photoshop, but you’re no longer going to have access to the raw frames unless maybe you somehow dumped them out into layers in Photoshop.

Pamela: That would be painstaking and awful, and don’t do that.

Fraser: That’s where you’re saying, “Don’t do that.” OK, OK, great… [laughing] and one of the users in the Google plus hang-out says that RegiStax is awesome, but as user-friendly as an angry porcupine, so you’ve been warned that it’s as user-friendly as an angry porcupine.

Pamela: And a lot of this software is as user-friendly as an angry porcupine. Occasionally, it’s as user-friendly as an angry hedgehog.

Fraser: Right. Like adorable, but still prickly. Um, yeah, yeah, well I mean, in a lot of the cases it’s made by programmers, by astrophotographers, attempting to roll their own solution and then they get to the point where, “Well, it worked for me, but I guess it would work for other people as well. Sure, I can share it with you,” and then somehow it turns into a product at some point, and you know how it goes.

Pamela: Photoshop is THE easiest to use of all these pieces of software.

Fraser: Photoshop is awful! So, that’s terrible; that’s not saying a lot. OK, well then let’s move on to that third methodology because I think that is the one that’s the most complicated, I think, in my mind.

Pamela: And this is the time that you separate the apprentices from the master sorcerers. When you have your FITS images coming off of a CCD…

Fraser: FITS images? What? What? Wha?

Pamela: So with your regular DSLR camera, you can get RAW, you can get TIFF, you can get jpegs. When you move on to using CCD cameras, it moves to an international image standard that works with all sorts of neat, nifty arrays and metadata, and it’s a great image standard that takes up lots of disk space, and it’s the standard we use for astronomy. It’s called FITS.

Fraser: FITS, OK…jpg, gif, FITS, sure. OK.

Pamela: And so once you have your FITS images, you have to do all of the nastiness that you had to do with your DSLR cameras, so your subtracting off your dark images, here we also have bias frames, so you’re subtracting off your bias frames, you’re creating your flat fields, you’re dividing off your flat fields. You are then image aligning everything, and to do all of this for free, you want to use software called IRAF that will make you cry. It’s pretty much a guarantee [laughing]. I’ve been teaching for Swinburne Astronomy Online for a number of years and once or twice a year, I have a student take on IRAF and I’d say that majority of them have either wanted to act violence upon their computer, or they’ve simply ended up weeping at their keyboard [laughing]. And the thing is, though, once you make it past the tears and the anger, and the denial, and you move on to acceptance, IRAF can do absolutely anything and it is completely free. It’s powerful — it just does miracles to bad images. Now, to those of you who’d like something a bit friendlier, we’re now back to the angry porcupine, or the angry hedgehog level of software. There’s a number of pieces of software out there. Maxim DL, which is the same company that does Maxim DSLR, they’re actually different versions of the same piece of software. There’s AIP4WIN, which has the best user manual out there. You can buy the user manual by itself, and it’s kind of the go-to manual in how to reduce amateur astronomy CCD data. There’s CCDSoft, there’s other kind of in-between educational professional and amateur software, there’s…Mira is a piece of software that’s out there, and for those of you who want to spend the big bucks, there’s software called IDL, which is kind of it’s own image language, so when you see these amazing color simulations of, like, asteroids hitting the ocean — that simulation was probably written in IDL, and you can also use IDL to reduce all of your astronomy data.

Fraser: Right, and so then we’re going to have…now is the CCD connected to the computer, is it going to be this again, dropping these great big images in FITS, these FITS graphics? And then you’re going to then import them in, and the software in, you know, is going to, you know, you’re going to be doing the settings, and setting: this is the dark removal, and that’s the this, and that’s the that, and you’re going to use all the settings depending on whether you’re trying to make a pretty picture, whether you’re trying to do science and come out with this, again, you’re going to come out with a final raw image, or are you going to come out with multiple images, which you’re then going to combine in Photoshop? What next?

Pamela: So CCD, if you’re using a highly-sensitive black and white CCD, looking through filters, which is what I’d recommend, you’re going to end up with an absolutely through-the-R filter, amazing combined image, an absolutely amazing, through the V or the G, something that gives you green colors image, or whatever set of colors you’re using. You’re going to get each of these different black and white images still in FITS format, and then there’s that little piece of software called FITS Liberator that’s available completely for free from the Hubble Space Telescope Science Institute. It’s actually put together by the European space agency, and this free piece of software is going to allow to take that FITS image and play with it until you get the stretch exactly the way you want it, until you get the white balance exactly the way you want it, and then it outputs it to something that you can use in Photoshop or Gimp. So we’re back to Photoshop and Gimp again.

Fraser: Photoshop and Gimp, right. And you’re going to import them in as one image or are you going to put them as three images, and then set one for your red, and one for your green and one for your blue, and then mess with it that way?

Pamela: Right. That’s exactly what you do. You import them in as individual images and then you copy them in to your different image channels. And one of the neat things about Photoshop is you can actually play with it such that we talked about while you’re taking images that you should take some unfiltered images that you use as illumination images. These simply allow you to sharpen things up in the end, so you can use that to mask the entire image using either a darkened or a lightened layering effect. You can then take and make your red channel some combination of images through a red filter and an H-Alpha filter, some combination of H-Alpha and IR, so you can combine five, six different filters into those three-color channels that we use for RGB in all sorts of creative ways that allow you to get these amazing images.

Fraser: That is really cool. That’s…and again, it’s the most complicated way, but again, it’s the way that gives you the most control at every step of the process, allows you to both do science and make pretty pictures if you want, and the final results are worth the effort, so I think that’s fantastic. Well, I think we’ve come to the end of our three-part trilogy on astrophotography, and I think we pulled it off. I think…

Pamela: I think we did.

Fraser: Yeah, I mean, talking about astrophotography… Seriously, we have had this show in the works for like 100 episodes, we’re like, “Yeah, we should do…we’re going to have to talk about it…how’s that going to work?” So anyway, I think that was great. I think, someone can have this on while they’re in front of the internet and be browsing for all these different pieces of software and pieces of gear, and take a look at it and check through our show notes. We’ll have links to lots of stuff, so I think that was great.

Pamela: And we’re sorry if we were a terrible influence on you, but I know this three-part series led to me buying a new Canon Rebel T3I camera, so I can go out and play along with our show. And for those of you who want to learn more and want to find a community of people doing this, the Cloudy Nights forums is a great collection of human beings who know their hardware, so…

Fraser: Well, I’m going to sort of shamelessly self-promote as well, which is that we post amateur astrophotographers on Universe Today almost every day, sometimes two a day, and we’re always hungry for people to send us the images. So if this has in any way gotten you inspired you to take some pictures, you know… We’ve highlighted everything from people showing conjunctions, and pictures of the Moon, they’ve just…or like a really nicely-framed image to the really high-end CCD stuff, so you know, if you want an outlet to do that, we’ve also got a Flicker group on just for Universe Today’s astrophotography. And if you come to Universe Today and look at any of the astrophotography photos that we post, you’ll see a link to that Flicker group, then all you’ll need to do is just post photos into that Flicker group, and then we will pluck them out and highlight them in Universe Today, so not only are we going to get you hooked on this hobby, but I’m also happy to promote you and get your name out there, so you know — get started!

Pamela: And Fraser’s not the only one doing this really well.

Fraser: Yeah, I am. It’s just me; it’s the only place. No, no, there’s lots of good stuff.

Pamela: The one other place that is my favorite random historical sites images to use for PowerPoint presentations is there’s a site called The World at Night – TWAN, and they have all of these amazing images of cities, of old architectural ruins, of those geologic features that appear in every geology book, so you have Ayers Rock in Australia, for example, so you get this combination of amazing things on the planet Earth, and amazing things in the skies above, so…

Fraser: Perfect.

Pamela: Lots of communities to join into…

Fraser: There’s tons, there’s Ice Hunters, which is Mike Salway’s community…yeah, there’s a ton. Even Flicker is great, Picasa, even on Youtube there’s some great stuff, so there’s lots of places to go.

Pamela: And Astronomy.net will put all of the metadata on your image, so that other people looking at your image know, “Oh, that’s this place on the sky,” so that’s a project by David Hogg, and they have plug-ins that work with Flicker.

Fraser: Sweet. OK, cool, well thanks a lot, Pamela.

Pamela: My pleasure.

Show Notes

• Astrogear
• Google+ — Pamela, Fraser
• McDonald Observatory
• Raw format and why — Northlight Images
• Night Sky Photo Tips – Dennis Mammana
• More tips from the One-Minute Astronomer
• Astrophotography Hints and Tips — EAAS
• How Image Stacking Works — Keith Wiley
• Webcam Astrophotography Tutorial for Planets — Ray Shore
• Using ToUCams for Astrophotography
• Cloudy Nights (Telescope reviews, astrophotography forum)
• Ice In Space Forum
• Filters for Astrophotography – Astropix
• Info about Hydrogen-Alpha
• Avoiding “square” stars (discussed in this astrophotography equipment primer by Starry Wonders)
• John Chumack
• Tom Davis
• True or False (Color): The Art of Extraterrestrial Photography – Universe Today

Transcript: Astrophotography, Part 2: Techniques

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Fraser: Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University at Edwardsville. Hi, Pamela. How are you doing?

Pamela: I’m doing well. How are you doing, Fraser?

Fraser: Doing really well, too. So you wanted to plug something…

Pamela: I did. It’s the Holiday season. We are recording on Thanksgiving Eve, and I know many of you are gearing up to give gifts, and if you have a kid, a comic book lover, or actually just about anyone in your life, we have roughly 1000 Hanny and the Mystery of the Voorwerp comic books, and we‘d love it if you purchased 1 to 200, so go to Astrogear.com, and we’re also going to be posting up new t-shirts and all sorts of stuff up there, so consider AstronomyCast as you’re doing your Holiday shopping.

Fraser: And the second thing is we are once again recording this episode of AstronomyCast as a Google plus hang-out, so once again, we have eight of our closest friends listening in to the episode, and correcting us as we make mistakes, and suggesting ideas that we hadn’t…hadn’t even occurred to us as we are doing the recording, so thank you to everyone who is with us today, and you get to see the way the show really gets done. But if you want to do…participate in joining us in the future, all you have to do is circle either me or Pamela in Google plus. Google plus is free to join, you don’t need an invitation, and then you can circle us, and then you’ll see the announcements when we’re about to do the episodes, and then you can join our hang-out and watch the show, and then hang out for, you know, usually half an hour afterward and we answer questions and talk about Space, or Thanksgiving, or whatever, so alright…Cool! Alright, well let’s get on with it then. So in the first episode, we talked about the gear you’ll need for your expensive astrophotography hobby. This week we continue our discussion and talk about the techniques you’ll use to get those amazing photographs. Bring a hot drink and get ready for some cold nights, but trust us, it will all be worth it. So Pamela, before we get into this, do you have an anecdote of, like, just some brutal astrophotography observing work that you’ve done?

Pamela: Well, so I study variable stars, and I got to use the 30-inch at McDonald Observatory when I was a graduate student and it has a 1-degree field, which meant that not only did I get the variable stars I was looking at, but I got everything in the field around it. And the awesome thing about doing variable stars is you take image after image after image after image, which is exactly what you do when you want to get high-quality astrophotography images, so I spent lots of nights out there, and was able to build some pretty awesome images, but one of the things was is you get into a rut occasionally, you’re sitting there, you’re at your computer, you’re taking image after image after image, and I was doing 600-second exposures and there was one point, I’m sitting there and the old man on the mountain, the engineer who babysat us made sure we didn’t destroy the telescopes or anything, came into the observing room I was sitting in, and he was just like, “What are you doing?” in the standard, you-stupid-graduate-student tone of voice. I’m like, “I’m taking images.” And just as he says that, an image comes onto my screen that’s completely starless. I am looking at absolutely nothing, and I look at him and he looks at me, and he just uses his hand to beckon me outside and I get outside and the entire dome is just like underneath this thick wall of clouds that came out of nowhere as near as I’m concerned, so it’s amazing how the sky can change in 600 seconds, and I felt rather foolish at that moment in time.

Fraser: So, right. So if you’d practiced some better technique, perhaps you would have noticed the fact that you were getting clouded out. And so last week, we talked about sort of the three main ways that you can do astrophotography. One is you take a really nice, you know, digital SLR camera, connect it onto a tripod and just do some really nice long exposure images. Ideally, track with the motion of the sky, and, you know, get those beautiful Milky Way images and star fields and things like that. The second way is you take your webcam, hook it up to the eyepiece of your sort of medium-level grade telescope, and get those amazing images of the planets and the Moon and things like that. And the third way is the, you know, the price of an SUV, where you hook up the CCD camera to your $20,000 Ritchey–Chrétien telescope and, you know, take some amazing Hubble-style deep sky photography. So then let’s go back and run through those different methods and talk about what are the kinds of techniques that astrophotographers use to get those kinds of images. And I guess, you know, we should probably start with the images, you know, the sort of long-field stuff or the long-duration, long with the DSLR camera. What’s your method to get the raw images?

Pamela: Well, the first thing you need is some sort of a camera that allows you to output in raw format, so that sounds kind of like, “Oh, of course it’ll happen!” but when you’re purchasing your DSLR camera, take that into consideration, and then remember to switch the setting.

Fraser: So, hold on a second here. You talk about raw format, and like I know that my Canon T3 will…I can take jpegs and I can take this raw format, and so I want to shoot with that raw format and that creates these monster digital files, right?

Pamela: Right, so what’s happening is when you use jpeg images, it does some sort of a compression. And basically what it’s doing is it’s saying, “OK, this set of pixels over here – they’re all the same color, so I’m going to store them together. This set of pixels over here – they’re all the same color; I’m going to store them together,” but when you store in raw format it actually stores the data for every single pixel separately, so it takes up a lot more space. It’s the difference between saying, “pixels 1, 10 – 20, 100 are all black, and saying 1, 1 black, 1, 2 black, 1, 3 black.”

Fraser: Right, so there’s a like a compression and loss of data.

Pamela: Right, so with raw you have none of that loss of data, and it allows you to keep all the information for every pixel — and you really need that for astrophotography.

Fraser: OK, but those files are BIG.

Pamela: They’re HUGE, but it’s worth it in the end. If you’re trying to get the best image you can, why start out by throwing away data as you’re taking your image?

Fraser: OK, so you’ve set these big, long exposure times, and how do you go through that process? How do you gather that much light?

Pamela: So there’s two different things that you need to consider: one is how long are you going to keep your shutter open, and the other one is how open are you going to make your aperture. Now, the two of them actually go together. If you’re going to try to take a short exposure of the night sky, open that aperture all the way out. If, on the other hand, you’re looking to take a five-minute or ten-minute exposure, you might want to close your aperture down just a little bit as you’re taking that full-sky image, so that light pollution, moonlight, um, all of these different factors don’t cause the sky brightness to look so bright that it suddenly appears like you’re taking a twilight image. As you take these long exposures, it’s amazing how much sky brightness you pick up. So one thing that you actually want to do is you want to play, to experiment. You want to try that 300-second exposure with the aperture one click closed, that 300-second exposure with it two clicks closed, and you really don’t want to go longer than 300 seconds, and you probably don’t want to go longer than 30 seconds unless it’s an ice-cold night and you’re far away from granite and no supernova has gone off recently. And the reason I say that is if it’s a warm night, then you’re going to run into problems with the heat of your electronics bringing up the background noise in your images as you take longer and longer exposures, and if you’re either in a very granite-rich area or there’s some other reason – a solar storm or something else that’s causing a lot of cosmic rays, those will cause all of these little, bright pixels in the background that are a pain to correct for, so by having reasonably short exposures, you don’t get as many cosmic rays per image, and you don’t…

Fraser: Are you kidding me? Is this like a joke?

Pamela: No, I’m not! This is a real concern.

Fraser: You’re actually telling me that I have to be concerned that cosmic rays and radiation from granite is going to put noise into my beautiful astrophoto?

Pamela: This is an honest-to-God problem.

Fraser: Really?!

Pamela: This is one of those things that drove me crazy as a graduate student because a single cosmic ray hitting a star blasts that star out of usability, so you’ve only wrecked one pixel, but that one pixel exploded that star’s values. Now, you can also get these glancing blow cosmic rays that cause stripes of bad pixels, and all these other annoying things, so yeah, you have to actually start worrying about cosmic rays, and the longer your exposure is, the more cosmic rays your exposure is going to have.

Fraser: If you say so…well, that sounds pretty weird to me. But, right, but what you’re saying then is it’s this balance between aperture and exposure, that you open up the aperture to pull in more light, and you don’t have to necessarily do as long of an exposure, or you can shut down the aperture and do a longer exposure, and there’s not going to be any one way that’s going to make the best picture. As you say, it’s about playing. It’s about trying one idea, trying a different idea, and see what works best for your sky, your technique. You know, if you set the exposure too long, it might blow out the Moon. If you don’t do it long enough, the stars are going to be too dim, so it’s just a matter of finding that happy medium.

Pamela: And there’s no one right answer because the Moon keeps changing in phase, everyone has a different characteristic to the light pollution — one night your neighbor has the light on, the next night they don’t – all of these things add up to chaos, but as you get practiced, you can look at the sky and say, “Ah, tonight I need to…” and you can do what you need to do. It’s like learning to play violin. You instinctually learn where your fingers go every time, and you can make adjustments for temperature and other things through tuning that you know how to do instinctually.

Fraser: Right, right…OK, cool. And so, you know, we talked about the gear, but essentially you will be messing with your aperture and your exposure length, which, you know, every camera is different where the setting is on that, and you will be recording your photographs as raw images and then attempting to dump these into your, you know, some way of…your repository, and you’re going to be processing it — and that’s a future show, that’s episode 3 if we’re going to talk about the processing methodology, but really it’s just about… I mean is there anything else sort of technique-wise except you go out, you set up your camera, figure out your happy place with your exposure and your aperture, and record those raw images?

Pamela: Well, I think the one thing you have to remember to take into consideration is it’s not one perfect picture you’re trying to take digitally because you can add things together. What you’re trying to do is get a series of images that aren’t overexposed, a series of images that have that black sky and are still showing the stars, and then you stack those images together, and by adding them up, well, you don’t have that many cosmic rays to worry about, comparatively, because you can take…one nice thing is you add them up and say, “Ah, there’s a cosmic ray in only one of these ten images,” and you can correct for it. If you only have one really long image, you can’t correct for it. So you’re going to add these images together, and it’s as you add them together later in that next show we’re going to have that you end up finding all of the nebula, you end up finding all of the faint galaxies. So your goal taking your picture is to keep your black sky and get as much light as you can while still having your black sky.

Fraser: And so even with those wide-field, you know, those beautiful images you see of the Milky Way rising up over some desert sky, you know, those are done with a series of shorter exposures that are then stacked?

Pamela: Yes.

Fraser: Or are they done with one big long exposure? So you wouldn’t do a big, long like minutes-long, hour-long exposure. You would take a series of shorter exposures in a raw format and then stack them on computer.

Pamela: Exactly. And the other thing about images like that is you’re worried about, well, the sky is rotating, and you can have your telescope set up perfectly, but no matter how perfectly it is, something is going to cause the tracking to not be absolutely perfect. Every telescope in the world there’s something that is correcting that tracking, and unless you have some sort of an auto-guide system, you’re going to slowly, over time have your stars drift, and by keeping your exposure shorter, you don’t end up picking up that drift.

Fraser: But even if you have some kind of tracking, like, if you’ve got your, you know, you’ve got it connected on an equatorial mount, your connecting with the sky, that’s still not the way to do it. The way to do it is to…

Pamela: It’s still not good enough.

Fraser: It’s not good enough.

Pamela: Over the course of minutes – and you’re going to be taking exposure after exposure adding up to minutes – it’s going to move one or two pixels, and that one or two pixels blurs your image.

Fraser: Makes it all blurry…yeah, OK, so we’re taking…so we’re going to capture, you know, even if we’re tracking, we’re going to capture a little piece of sky, and then we’re going save that file, and then…and our camera might be tracking the whole time, where we take a little picture, take another little picture, and just build up that, OK that’s perfect. OK, let’s talk about that second method then. We talked about the…where you’re taking the planetary astrophotography, where you’ve got your mid-range telescope, and you’ve connected your eyepiece, you’ve connected a cheapo webcam up to your eyepiece, and you’re then capturing image after image after image. So what’s the process there?

Pamela: So here it’s often a matter of getting rid of as much light as possible. This sounds really strange, but when you’re looking at Jupiter, when you’re looking at Saturn, you’re looking at something that’s going to saturate your detector, and so sometimes you end up having to do crazy things like putting a cardboard cut-out on the front of your telescope. So, what you want is to have in every single frame a not-fully-saturated Jupiter. Ideally, you want to know at what point does your detector stop catching light. So there’s usually numerical values associated with every pixel. The CCDs I’ve used have usually gone from zero, which is absolutely nothing, to around 5,000 counts, they really stopped functioning, and so you need to figure out what’s that count at which it stops functioning and come about a third below that is where you want your maximum pixels to go. That way you can get a full dynamic range, you don’t have to worry about blowing out your detector, and there’s other things like where is your detector linear? Now, for pretty pictures you don’t have to worry about that as much, but the idea is…ideally, you double the number of photons that hits a pixel and you double the brightness. Well, at a certain point, that pixel starts to fill up and you just can’t add enough more photons to it to double how much it’s detecting, and it loses sensitivity that… there’s a whole bunch of other stuff, and I’d start to have getting into quantum efficiencies and that’s beyond us right now.

Fraser: No, I’d like to go into that…but no, no, but I guess the part that I don’t really follow then is, I mean, you’re taking your webcam, and you’re putting it onto your eyepiece and then you’re just letting it run, right? You’re just recording like the highest quality video that you can get, and then you’re putting stuff in front of your screen, you know, some kind of cardboard cut-out in front of your screen, you’re turning up and down the color balance, the “gain” of the camera itself to get that perfect happy medium, but then how long are you just letting it collect for?

Pamela: As long as you can.

Fraser: Like, hours?

Pamela: Sometimes, it depends on what you’re trying to do. So, I’ve seen amazing videos that are taken where…so with Jupiter, the planet’s kind of rotating, and if you go for hours, you can build up movies of the rotation of Jupiter, but if you just want a stunningly beautiful picture of Jupiter, there you just want to go a couple of minutes, and if you’re taking several frames a second, a couple of minutes is going to give you more images than you know what to do with because the catch for using a webcam is after you’re done capturing this video, you’re going to go through it frame by frame by frame looking for the sharpest images, and you’re going to throw out the ones that aren’t sharp.

Fraser: Right. And that’s again talking about technique, but yeah.

Pamela: So, here as you take your images, pick a nice beautiful night, get everything so that you’re not saturating your images, and take a few minutes of frames on Jupiter, if you want to do that entire movie of its rotation, take a couple of hours, but if you just want a pretty picture, you’re just looking at a couple of minutes of video.

Fraser: Right, so you’re going to take a couple of minutes, you’re then going to, yeah, you’re then going to go through them frame by frame, so a couple of minutes is probably enough time because if you go longer than that in the case of, say, Jupiter, the object is going to have rotated and then that’s going to introduce blur and more problems into it as well. So it’s more about getting a whole pile of good frames you can then stack later. OK. Awesome.

Pamela: And this works for Mars, less blocking of the front of your telescope required, and Mars is particularly tricky because it’s very tiny, so you want to push what your telescope’s capable of doing. So this is where you want to get as much magnification as your telescope can support and as short an exposure as you can possibly get on your video camera. So wait until Mars is at its closest point to the Earth; wait until it’s at opposition, and give it a try and you’d be surprised what you can get. Looking at it with your eye, your eye doesn’t have the time resolution your video camera has, so you can get a sharper image with your video camera and then add all of those frames together and you can actually make out the icecaps, you can actually make out the volcanoes and the valleys. It’s really quite amazing what you can do.

Fraser: Now, are you recording it in any special way, or are you just recording it straight in whatever color sensitivity your webcam wants to do? Like, do you need do it in black and white, or…?

Pamela: So, what I’d recommend is actually getting a black and white, low-light security camera or getting one of the two-cans, two-cams rather. The two-cams are the ones that are preferred by most astrophotographers, and I believe that those come in both black and white and color, and just follow the user’s manual for your particular camera. One of the things that we run into as a problem with this show is technology is constantly changing, so I’m trying to talk generically, but where the technology’s constantly changing, do what’s recommended for your particular camera. Avoid compression as much as possible, and try and save things in as raw a format as you can.

Fraser: Right, so you’re going to get…whenever you’re listening to the episode of this show, go and lurk around the astrophotography forums and find out what webcam people are currently recommending.

Pamela: Cloudy Nights is an awesome place to go talk to people.

Fraser: Yeah, and/or IceHunters, which is Mike Salway’s forum. Yeah, so that’s to get that latest gear. We try to be timeless with this episode. Now, what about filters? We didn’t talk about filters with the taking night sky, wide-angle stuff because you’re just going to be using your camera with its different lenses, but are you going to want to use any kind of filter when you’re doing the planetary stuff?

Pamela: When you start getting into been-there-done-that-let’s-see-what-I-can-do-that’s-the-next-step-up, that next step up in webcam work is where you start buying the filters. You can get filters that can accentuate the icecaps on Mars, that can accentuate the banding on Jupiter, but the place that filters really start to change your perspective on the sky is when you go that next level, to the “SUV’s worth” of equipment, when you have that full CCD detector and when you have that either Schmidt Cass or Magneto Cass or Ritchey–Chrétien telescope.

Fraser: I know the filters are really important for the deep sky stuff with the CCD, but do the filters come into play with any of the planetary stuff?

Pamela: They can if you’re trying to accentuate filter, when you’re trying to accentuate features, but they aren’t going to help you get that true color image. Now, what you can do is if you’re in a very light-polluted area, there are some filters out there that specifically try to filter out the light produced by sodium lights, that specifically try to filter out some of the other compression lights. As we use more and more fluorescents, it makes it easier in some ways to filter out the light using narrow-band filters, but in general, if you’re trying to get a pretty true-color image, you’re not going to get it with filters. If you’re trying to look at specific features, if you’re trying to pull out the icecaps, pull out the valleys, that’s when using the filters can help.

Fraser: And I know that some people use this technique for observing the Sun, and so obviously then you definitely want to get some solar filters.

Pamela: Yeah, you don’t want to look at the Sun at all without a filter, and so there you’re looking at one of basically two different things. You can get what’s called a neutral density filter, which blocks all colors of light equally, and so you can get a neutral density filter that blocks 90% of the light in all wavelengths. You probably want to go even more than that when you’re looking at the Sun. Now, the other direction you can go is you can get something called an H-Alpha filter, and that’s a filter that only lets through the specific transition called H-Alpha in the hydrogen atom. This is one of the bomber lines; it’s the one that allows you to see all of the neat corona, loops, and storms, and it accentuates sunspots, and if you have enough magnification it actually allows you to start seeing the convective cells on the surface of the Sun. Now, if you just go with a neutral density filter, all you’re going to see is the sunspots and the bright stripes, the faculae that are caused by coronal loops, but with the H-Alpha you can start to see details in everything.

Fraser: OK, so I think we’ve kind of wrapped up the techniques for that second method. And the third method, and I think this is the one you know the most about, is the deep field, you know, big telescope, CCD camera connected to it…how on Earth do people get these amazing photographs?

Pamela: Lots and lots of patience and tracking, and the really, really best ones – what you’re actually doing is you’re sitting there, and you either have a second CCD chip that’s auto-guiding your telescope, or you’re sitting there with a hand paddle guiding your telescope as you watch a video screen output. It’s like playing a video game of keeping the star on the target. Nowadays, a lot of times the software will do it for you, but when I was a graduate student, there was hour after hour of moving the telescope… Literally, you’re pressing buttons, and it’s just like the slowest-paced video game EVER. So you’re making sure you’re staying precisely on the star, or on a bright object in the field that you can put crosshairs on to make sure that you’re staying focused, or staying pointed. You perfect focus, you very slowly step through and make sure you can’t move a hair in either direction without making your stars become bigger blobs, so once you get your focus just right…and you can’t…you actually have to be careful that you don’t end up with square stars. This is going to sound really strange, but if you’re on a telescope with a really large field of view and the atmosphere is perfect, when you get the telescope completely in focus as perfectly as it can be focused, sometimes the stars are one pixel in size, and that is unappealing and you can’t do anything with it scientifically, so there are actually rare cases where you have to un-focus your stars slightly to make sure that they spread out across enough pixels. So it’s this black art of if the stars are big enough, focus the telescope so they can get no smaller. If you do that and you have square stars, un-focus. So you play with focus, get it perfect; once it’s perfect, you then start taking exposures. You want to have your exposures long enough that the sky stays black, but you’re starting to get whatever faintness that you’re looking for, whatever nebulosity, whatever arms on a galaxy, and you’re not getting too many cosmic rays, so usually the longest you want to try and push is about 900 seconds for a perfect system. After 900 seconds, the number of cosmic rays just becomes annoying. Most systems you actually want to stay down around 300 seconds, so you get those 300-second exposures, and you do it one filter at a time. With these high-grade CCDs, the way you get extremely good resolution is all of the pixels are simply sensitive to light/no light, and so everything you do is black and white images. If you were getting color images, there’d actually be triplets of pixels that are sensitive to the red/green/blue of a color CCD. You get more resolution by doing black and white, so then to get color, this is where the filters come, so you actually put the red filter, the R filter, the whatever filters that you’re using filter on, take the exposure. You then put the next filter on, and here’s where it becomes a black art because your CCD is differently sensitive to light in different colors, so you might find, “Oh! Everything is starting to saturate! I’m starting to get to the point where I’m blowing out my CCD at 200 seconds in red. Now, I put the green filter on and — oh, crud! At 250 seconds I’m starting to saturate!” So you have to figure out how do you play with the exposures, and that’s also going to vary with, well, what are you looking at? Is it a blue galaxy? Is it an oxygen-rich nebula? Is it a red reflection nebula? All of these different (or a red transmission nebula, rather)…all of these different things you have to adjust your filters, you have to adjust your exposure times for.

Fraser: Wow! That’s like way more complicated than the other methods. It’s funny how it all scales up. The gear’s more expensive and the method is a lot more complicated, but at the same time, you know — greater risk, greater reward. I mean, you see some of those pictures, again, some of the best…guys John Chumack, there’s a lot of them, Tom Davis… they produce these photographs that look like they came from the Hubble space telescope. Their ability, their technique is so good that it’s just astonishing. So they are targeting that sweet spot, that you have the CCD hooked up, you get your filter on, you capture for 300-ish seconds and then store that image, that long-exposure image, but it’s going to be like take one image, and then take another one, and then take another one, and then take another one, and then we’ll talk about technique next week, or I’m sorry, about post-processing, but essentially you’re stacking all those images together try and just keep…you’re taking long-exposure after long-exposure and then creating a super long-exposure with all of those together, and if you’ve done your job right, you’re going to get those beautiful faint, the nebulosity, the galaxy, the dust in the galaxies and all the beautiful pictures that come with astrophotography.

Pamela: And if you’re just after pretty pictures, one of the really awesome tricks I learned from an amateur astronomer (because you can’t use this data for science) is one of the tricks for bringing out all the details is remove the filters — all of the filters — from your camera, and create what’s called an illuminance image. This is where you just capture as much light as you can to get the details, and then you use that as a mask in your final image, and if you’re struggling to get enough light of a really faint object, when you then put your filters on, you can do what’s called binning the CCD. This is where you combine the light that’s hitting every four pixels into one, so that’s a two by two bin, or you bin all the light that’s hitting every 16 pixels into one – that’s a 4 by 4 bin, and this allows you to get deeper images faster, and that’s particularly useful if you’re just not that sensitive a set of equipment. So you then put your red filter on, bin your CCD get all of your red light, put your green filter on, bin your CCD get all of your green light, and when you stack it together later, you’re able to resurrect all of that detail using that illuminance frame. Now, if sensitivity isn’t an issue, then you go the other direction, and you just do everything through filters, and you start playing with what are called narrow-band filters. There’s two types of filters: there’s broad-band filters and there’s narrow-band filters. Broad-band filters are like, “I want all the shades of red. I want all the shades of green.” Narrow-band are, “I want the light produced by the H-Alpha transition. I want the light produced by the specific oxygen lines produced in planetary nebula that are green.” And here you’re looking to bring out specific scientific neatness, awesomeness details by which filters that you’re using.

Fraser: Yeah, and the terrible truth of astrophotography with a lot of the scientific stuff, the stuff from Hubble, is the pictures are completely fake. They’ve, you know, they’ve used one very narrow-band filter for one color, they’ve used another very narrow-band filter for a completely different color, and then a third one, and then they go that one is red, that one is blue, and this one is green, and then they merge them together and you get a…what looks like a beautiful colorful photograph, but actually has nothing to do with what the object really looks, and again, I think, this comes down to your experience. Are you trying to create a realistic view of what the object really looks like, or are you trying to create a very beautiful picture? And if you’re trying to create a very beautiful picture, you’ll want to learn which of those narrow-bands are going to give you the right combination of colors to make your image look beautiful — and you will be part of the lie.

Pamela: [laughing] Well, it’s not always a lie, sometimes it’s…

Fraser: No, it’s not always, but I know with a lot of the stuff with the Hubble and stuff that they aren’t going for true color.

Pamela: Right. Right. What I love though is sometimes the universe just works and a lot of these nebula where you’re looking at specific emission lines of gases, you get your oxygen narrow-band filter and that’s green, and really that’s all the green the nebula’s producing. You get your hydrogen filter, and that gets you the red, and really that’s all the red that’s being produced, and by using these narrow-band filters, you’re able to basically get rid of a lot of the background goop, and strictly see the light of the nebula.

Fraser: Very cool. Well, I think next week we’ll go into the whole other half of this project, where you sit with a computer and process, process, process to get those final products that people see, so that’ll be great. Alright well, thanks a lot, Pamela.

Pamela: That sounds great. I’ll talk to you later, Fraser.

Show Notes

• End of the World…. (Not!) Cruise
• The World At Night (TWAN)
• Nikon Vs. Canon DSLR cameras for Astrophotography — AstroPix
• Tripods/Mounts for Astrophotography – AstroPix
• Oceanside Photo and Telescope
• Aperture and shutter speed — Cambridge in Colour
• Lenses and Zoom for Astrophotography – AstroPix
• Webcam Astrophotography Tutorial for Planets – Ray Shore
• Using Webcams for Planetary Astrophotography — Schmidt-Cassegrain website
• Clay Center Observatory
• Ice In Space
• Mike Salway
• Thierry Legault
• Guide to CCD Imaging — Starizona

Transcript: Astrophotography Part 1: The Gear

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Fraser: Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University at Edwardsville. Hi, Pamela? How are you doing?

Pamela: I’m doing well. We’ve hit that point in Fall where you know winter is coming, but it’s still beautiful. I hope you’re having similar weather there in the Vancouver area.

Fraser: Absolutely. The La Nina year that we’re having has made it just non-stop sun all the way through September, October, November…it’s been amazing. Makes up for that horrible summer that we had. So we got an announcement today, which is that we’re going to be going on a cruise to celebrate the end of the world, which is as you know, we love to rant about the 2012 “end of the world” prophecies, and so on December 21, 2012 we will be in the middle of the Caribbean visiting Mayan ruins, laughing at the fact that the world isn’t ending, and you can come with us. So here’s the details: it’s called “The End of the World Cruise,” or “The Great 2012 Not the End of the World Cruise,” and it starts on December 16-23, 2012 on the Norwegian cruise lines’ Norwegian Jewel, and so there’s…David Brin is going to be the headline speaker, we’re going to be doing live episodes of AstronomyCast, we’re going to be doing demonstrations of astronomy, bringing telescopes… Come meet us, hang out with us, get sick of us, get sick with us, but uh…yeah, but we will be doing that, and you can join us. So you can go to end-of-the-world-cruise.com, and you can sign up. And you want to let them know that you signed up because of us. So how does that work?

Pamela: Well, so actually, they don’t even need to go to that website except to get details. Everything you need to know is going to be on a special link off of the AstronomyCast website, and the way it works is there’s this wonderful woman by the name of Zelda, who’s our reservation specialist, and the only way to book for this show, not for this show, well there are shows, book for this cruise is to give Zelda a call and tell Zelda, “AstronomyCast sent me, and I want to celebrate the end of the world,” and she’ll set you up and help you figure out how to join us onboard. Prices range from $600 to a little over $1000 plus taxes and port fees, and we’re really hoping to see you.

Fraser: And it’s very important that you say that AstronomyCast sent you because if we want to be able to do this kind of stuff in the future, it’s important for people to know that AstronomyCast listeners want to come on these kinds of activities and do these kinds of cruises and trips and things like that, so please let them know that AstronomyCast sent you, and, you know, drop us an email if you want more details. I suspect it’s going to fill up pretty quick, so you might want to commit pretty soon.

[“Audible” commercial]

Fraser: Alright, well let’s get on to this week’s episode. Now, there’s a saying…I forget what it is, but talking about astrophotography, or doing a radio show about astrophotography is kind of like dancing about architecture, so we have put off this show for a very long time because we keep going, “well, you know, if it was video or we had photographs to show, then that would make things a lot easier,” but I think that we’re going do it anyway because a lot of people want this information, and your brain is filled with knowledge, and we will have great show notes and people can follow up afterward. So, let’s talk about astrophotography. So here we go… No matter how good your telescope is, you’re never going to see the same detail and colors as the photographs. To take amateur astronomy to the next level, you really need to attach a camera to your telescope. Welcome to the hobby of astrophotography. Fair warning: this hobby could bankrupt you! Alright, so then when we…and in this episode we really want to talk about the gear, so whenever people talk about astronomy to me and they, “Well, I looked through a telescope and it just didn’t look anything like the photographs that I see on the internet or taken by the Hubble space telescope…” So what is the gear that’s being used to capture those images? To take your first astrophoto, what is the chain of gear that you need?

Pamela: So it really depends on what you’re trying to take a photo of. There’s basically three different technology routes to go depending on your favorite target. So the folks that are out there taking these amazing images of the planets, who are taking these amazing images of craters on the Moon, of just a whole variety of stuff, mostly in our solar system, what they’re actually using is webcams. Two-cam webcams are the webcam of choice, and what they’re doing is taking a ton of images, finding the best ones and stacking those together. Now, on the other side, if you’re target of choice is wanting to instead get the horizon, and get constellations, and just bring the whole picture together, this is the work that The World At Night (TWAN) has done amazing photos. What they’re using is just off-the-shelf DSLR cameras, so that’s a different route to go.

Fraser: Or those beautiful time-lapse ones, those are done with DSLRs as well.

Pamela: Right, and then the third direction to go is you’re going to take that amazing deep image of a galaxy. You’re going to take the image that looks like it belongs on the cover of Sky and Tell discovering the star-forming regions. Those are people who are generally picking up CCDs, Charge-coupled devices, that they plug into the back end of their camera. Now, in some cases, you can use DSLR cameras to do that as well, so you have options.

Fraser: Right, so the chain is a camera, and in this case, if you’re going to take like wide-angle stuff, where it’s not through a telescope, just the camera alone is going to do the trick, but you need to be able to open up the aperture and let it…and all to have some way to track, right?

Pamela: Yeah.

Fraser: …the stars…that’s sort of step one, or you’re going to get the star trails. Step 2 is you’re going to need some kind of telescope that you can then magnify and then, and so the camera options vary, the telescope options vary, and then you mix and match to get the different kinds of results. So let’s just start then with just the simple you know, the DSLR route to get the beautiful, wide-angle, majestic you know, panoramas of the night sky with the Milky Way above, and you know, the desert landscape in the background. What kind of gear are we looking at there?

Pamela: OK, so we’re saving software for a different show just to make it clear for all those amateur photographers out there going, “But you didn’t…” We know. That’s coming later. So the basic starting point is buy yourself (and I’m going to show manufacturer favoritism here, don’t shoot me)…buy yourself the most expensive Canon DSLR camera you can justify, and then get yourself a solid, heavy-enough-that-you-don’t-want-to-lift-it-but-know-you-have-to tripod with tracking, and the reason that you need this combo is if your tripod doesn’t work well, your images aren’t useful, so you need this amazing tripod that’s going to just keep you locked on the sky, and then you need this amazing camera because, well, electrons don’t like to stay put, and if you buy a cheap camera, as the photons build up on that CCD or CMOS chip inside the camera, they’re occasionally going to try to jump to somewhere else on the image and that creates background noise, and you get the lowest noise, currently, using Canon cameras.

Fraser: So if I get that really nice Canon camera, or the Nikon equivalent, we understand that Nikons are just as good, and we don’t want to make this a religious war, but you take that Canon 5D and you go out with a nice, wide-angle lens on it, and if you just take a picture of the night sky, you’re not going to get a good picture. It’s going to be…you’re just not going to get enough photons from the stars. If you’re really lucky, and you’ve got the aperture wide-open, and you set the exposure length for a really long time, you might get some stars, but it’s not going to be that same level of quality. It’s all about the mount and the tracking, so where does that come from? I mean, I think most of us can go to Best Buy or Future Shop and buy that Canon camera, but it’s that tracking. Where does that come from?

Pamela: So here my favorite people to go to is Oceanside Photo and Telescope because you can basically say, “I have this much money. What can I get?” and they will point you in the correct direction. If the sky is the limit, there are people out there who are doing things as insane as mounting normal everyday cameras on Paramount mounts, which are $15,000, but at the other side (and they’re usually actually mounting the camera on top of the telescope on top on the $15,000 mount), but on the other side of that you we have people who are spending $100-120 and getting something perfectly reasonable, and when you spend the lower amounts of money, often what you end up doing (and this is a completely valid thing to do) is you take a whole bunch of shorter exposures, and you add them together, and in the end, you do want to be taking shorter exposures, but shorter can be 30 seconds, or it can be 5 minutes. What we found doing telescopic exposures was in a perfect world, you want to take as many 5-minute exposures as possible and then add those together.

Fraser: Right, and this is the “technique” discussion that we’re going to have in a separate…in the next podcast. Right, so I can take my…but my camera needs to at least be able to let me manually control the aperture, right? Like the exposure time…?

Pamela: Yes, so there’s two different factors that you want to be able to control. One is the aperture, which tells you how wide the shutter opens when it’s exposing the CCD. This is basically saying how much light you get in. If you’re looking at a human eyeball, your pupil is your aperture, so when someone is in a bright light condition, your pupil shuts down, and when you’re in a dark condition, the pupil opens up, so you need control over the aperture. You’d think, “Hey, it’s night sky observing, just open it up all the way.” But I’ve done things like take images during meteor storms when there is a little bit more Moon than you might want, and so I closed the aperture down a little bit so that I could get longer exposures without washing the sky, so these are things that you want to play with. So on one hand, you need to be able to control the aperture, and on the other hand, you want to be able to control how long the shutter is open for. You want to be able to say, “Figure it out for yourself.” And a good camera can actually take a fairly good night sky image for you without you having to do very much, but on the other hand, you want to be able to say, “No, do five minutes. I want you do to five minutes.”

Fraser: Right, and so that comes together to give you sort of as much control on it, and the experimentation is interesting because I definitely would have thought to just open it wide, you know, wide-open, as wide as it will go, but I can see that constraining it down a bit depending on the light, depending on what you’re seeing can make more sense.

Pamela: And it also depends on what you’re trying to do. I have to admit, most of my astrophotography days were with film cameras, and I’m a CCD junkie, and some of my favorite photos to take were things like star parties, where I’d take a 30-minute to one-hour exposure with the aperture not all the way open so that I didn’t wash out the sky, and I didn’t get blasted when someone with their red flashlight walked by because I was trying to capture the motion of the people in front of the camera. I was trying to capture the star trails in the sky. It all depends on what you’re trying to do. It depends on how bright the Moon is. It depends on do you have aurora borealis that you’re trying to cope with? Are you trying to capture motion over time where you’re going to keep the aperture open forever? So you need both. Now, one other tool that goes in with this is with a lot of these cameras, they have remotes that allow you to not actually be touching the camera when you open the shutter.

Fraser: Yeah, and they’re not very expensive and, you know, sort of a good thing to get anyway for a digital SLR camera.

Pamela: And some of these remotes allow you to tell your camera, “Take an exposure every five minutes,” allow you to tell it, “Keep the shutter open until I tell you to close it,” so that you can take control. That’s particularly useful if you’re trying to get nighttime lightning shots when you don’t know when the lightning’s going to come, so you just sit there and you wait, and you control the future of your camera.

Fraser: And so, you know, key words we’re looking for…and most of the high-end DSLR cameras will let you do this: that you can control the exposure length, you can control the aperture, so that’s the actual body, the technology of the camera. Now, what about the lens? What kind of lens do you want?

Pamela: Yeah, it depends on what you’re trying to do. The good, generic, I-don’t-know-what-I’m-going-to-do lens is to get something that goes from as small a number as you can afford to as high a number as you can afford, and this is where you start to see things that are, for instance, from 18 to 100-and-something, from 22 to 55. The two double-digit number to another double-digit number – that’s pretty much what you’re used to on your cheapo cameras. That allows you to go from being able to see the full room that you‘re in at a wedding, for instance (this is where most people end up experiencing their camera for the first time), to zooming in and just getting the wedding couple up at the banquet table when you’re in the back of the room.

Fraser: Right.

Pamela: Now, if you want to be able to start zooming in much more to, for instance, fill your frame with the Moon, this is where you need to start getting into triple-digit zooms.

Fraser: Right, so if you’ve already got one of these digital cameras, these fancy digital cameras, and many of them do, if you’ve got a Canon T2 or a T3 or a 5D or the Nikon equivalent, then you’re 90% of the way there. You just need to get a mount with an equatorial mount that has this motorized tracking that will then let the camera turn as the Earth is rotating and keep the stars in the same position as it happens, and then do some experiments. Try the Moon, try the planets, try interesting wide-open parts of the Milky Way, and you should get some beautiful pictures, you know, with some experimentation, and the techniques that you’re learning should serve you really well. So, you’re saying $100, $200 to get a mount like that that will do that kind of tracking?

Pamela: To get the cheapest, barely functional tripod that will just barely make you happy, and you’re buying something used — that’s where you’re looking for a couple 100 dollars.

Fraser: OK, so that sounds great, and that I think a lot of people…they don’t realize. They’re ready to do astrophotos, they just need that one last little investment. So then, that covers one whole section of astrophotography, but you talked about the three, so let’s talk about the planetary stuff, right, where you’re connecting a webcam up to a telescope. So we’re going to need that mount, same mount. We’re now going to need a telescope, that we have attached that now, you know, we’ve talked about telescope in the past — a few hundred dollars, but then we need like a webcam?

Pamela: Right. So here you blow your wad getting this amazing telescope, getting an amazing tripod, getting some sort of a tracking system, you’ve spent $1500 or more, $15,000, $30,000 easily, and then you go out and you spend $100 or less getting some sort of a webcam. Lots of people use two-cam webcams — there’s a whole bunch of other ones out there. And the idea is with the webcam, you’re taking image after image after image after image, and as the sky constantly varies, sometimes you get moments of absolutely amazing scenes, and sometimes you’re like “that’s a blurry blob. Someone sneezed on my telescope,” and by systematically combining all of the most amazing images taken by the webcam, you can build up these highly detailed images of these really bright planets. This only works with bright sources like planets where you can get enough photons in that one frame that the webcam records, but the folks doing this are able to do amazing things. One of my favorite sites to go look at is the Clay Center Observatory at Dexter Southfield High School. They’ve taken images of the International Space Station; they’ve taken images of Mars passing behind the Moon that are absolutely to die for.

Fraser: Yeah, my favorite community on this is a place called IceInSpace and the guy leading that is a guy from Australia name Mike Salway, and he takes pictures of Jupiter that you would swear came from the Hubble space telescope.

Pamela: Yeah.

Fraser: They are unbelievable — how good he can get those pictures and it’s amazing, I mean, he’s got a good, I think he’s got an 8-inch telescope, good mount, but the trick is that he’s mastered this technique of using the webcam, and then stacking the images, and we’ll talk about that in the next show, but the point being, you know, you’ve got that really nice tripod, that great equatorial mount, you’ve popped off your digital SLR camera, and you’ve plunked down your telescope of reasonable quality – it doesn’t have to be an insanely great telescope, and then you’ve got that webcam that’s taking that video through the eyepiece, and that’s how you get these amazing pictures, and it is, you know, best bang for your buck – an amazing way to do astrophotography.

Pamela: And what’s neat is with this technique you can also do things like get images of asteroids that are passing through your field, you can get timings of when asteroids occult stars, and so there’s so much different science that you can do while also getting amazing images.

Fraser: And there’s another guy, I’m going to mispronounce the name, I think, Thierry Legault, who is…he is from France, and he does time-lapse images of the International Space Station, the Space Station passing in front of the Sun, and he’s gotten…you know, you can see the solar rays, and you can see every module on the Space Station, you can see when the Space Shuttle’s attached to it. He’s done images of various satellites that are tumbling and about to re-enter the Earth. It’s quite an amazing hobby, and again, it’s not that further along. If you’ve already invested in the telescope, you’ve already got the equatorial mount, it’s just a few hundred bucks more to move down this road as well. It’s a really rewarding hobby. Let’s move on to the final stage of this hobby, and this is the part where you get bankrupted, which is where you’re trying to produce those beautiful deep field and nebula and galaxies and clusters of stars…and that’s where you start to spend the big bucks.

Pamela: And this is where I’m reminded that research shows that a hard-core hobbyist will spend as much on their hobby as they spend on their car. And I have to admit as someone who rides horses, that’s about true, given the fact that my car is a 1998 Jeep Wrangler, and I’ve had my horse for enough years that it’s had time to acquire value, I guess, is the way to look at it.

Fraser: Yes, I’m obsessing over a $10,000 mountain bike, so…

Pamela: Right, so we each have our different hobbies, but for the astrophotographers, this is where you get the guys and the gals out there who are spending $15,000+ on a Paramount mount, on a DFM mount, on something from astrophysics that tracks like any professional system, where they’re building the domes, where they’re getting the 20-inch Richy-Cretiens for their backyard, and then they’re dropping a few $1000 on a CCD camera, and soon they have something the size and cost of an SUV.

Fraser: Right, it’s a, what, a $10,000 mount, a $10,000 telescope, couple of $1000 on the camera, plus your dome, plus the remote equipment, plus, plus, plus…I mean you’re looking at about $20-30,000 to do that, but to just do the entry level, again, couldn’t you take your equatorial mount, your reasonably good telescope, and then…? But the point is you’re pulling off that webcam, and you’re putting on that CCD.

Pamela: Right, and you can do a starter system with everything you need for $5,000, so mount, plus telescope, plus CCD, plus the computer you need to go with it — $5,000 to get bottom-of-the-line, I’m-going-to-figure-out-if-I-want-to-do-this-and-make-it-so-that-my-spouse-doesn’t-totally-kill-me-for-the-amount-of-money-I’m-about-to-spend.

Fraser: And so you’d be very happy with the amount of imagery you’d be doing at that point.

Pamela: Right, and this is where you can start doing things like sitting on a target, and you use a completely different technique at this point, so you also have to now start to buy little pieces of glass. So CCDs, the really good CCDs are only black and white imagers, they go photon/no photon – that’s all they care about. But it’s the fact that they only care about photon or no photon that allows them to be so sensitive and have such high resolutions because they don’t need to leave space for other detectors that are sensitive to red and green if they’re sensitive to blue. Instead, all of the little detecting bits are crammed together simply doing photon/no photon, and you choose what color you’re looking at by going out and buying a piece of glass. So you’ll use a red filter to get the amazingly high-resolution image of just the red light coming from that object, you’ll use a blue filter to get the blue part, and you can buy filters that either allow you to capture specific types of gas — the oxygen lines, the hydrogen-alpha lines — these are narrow band filters, or you can buy broad band scientific filters if you’re interested in starting to do photometry, and you can still do beautiful color images with this – that’s what Hubble does. You can also, then, buy the flat-out ham of photographer filters: the red/green/blue filters, as well.

Fraser: Right and so it’s the different glass in each filter is going to cost you some money, the CCD, the quality of the telescope, as we said, this gets expensive, but about $5,000 to take a good crack at it, and I think you can probably get a taste of it. I mean, if you…the webcam probably isn’t going to make you happy, but if you could probably get an entry level CCD in there and get a taste of it. Just attach that to your existing…if you’ve got a good telescope with an equatorial mount.

Pamela: And the reason that you want to go for the CCD instead of staying with your DSLR camera is the CCDs have their electronics cooled, and I mentioned early on in the show that electrons don’t like to stay put. Well, if you cool them down, they move around a lot less, so if you start getting into a system that is either thermo-electrically cooled, or if you spend a lot of money, you start getting a system that’s cooled with liquid nitrogen — these systems are able to suppress what’s called “dark current.” This is the flow of charge around your detector simply because the sucker’s turned on, and by suppressing that dark current to the point, in some cases, of being barely there and detectable at all, you are able to get much longer images with much less noise in the image.

Fraser: Very cool. Alright, well, that was…I think that was good, Pamela. I mean, I was nervous that we wouldn’t be able to talk about something that’s all about photography, you know, imagery, but I think that was really good. I think that was really helpful and gave people a good idea of the landscape. Next episode, we’re going to talk about the techniques, so what are the ways that you actually will set up your camera, set up your telescope, places to go to actually get the imagery that you might see in the magazines and on the internet. So that was great! Thanks a lot, Pamela.

Pamela: My pleasure.

Fraser: Talk to you next week.

Pamela: OK. Bye-bye.

Show Notes

Transcript: Celestial Navigation

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Fraser: Welcome to Astronomy Cast: our weekly facts-based journey through the Cosmos where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain. I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University-Edwardsville. Hi, Pamela! How are you doing?

Pamela: I’m doing well, and a month from December 13th – fictional date – I’m going to be at the AAS meeting in Seattle, WA, and we will be doing an event called “Astrozone,” so you can goolge “Astrozone” and come out and take a look at us and see what we have to show you, if you’re interested.

Fraser: Now, what’s funny about this show is that both you and I will be taking cruises — separate cruises, you’re going with your husband, I’m going with my family — half a hemisphere apart. You’ll be in Europe and I’ll be in Miami, but you know, navigation at sea…I thought it would be a good opportunity to talk about celestial navigation.

Pamela: All I have to say is I’m really glad we have GPS.

Fraser: You know, I picked up a sailboat and I’ve been kind of going through all the learning, and there’s whole, huge sections about how to do celestial navigation. I’m like, “Why bother? Just get a GPS.” I’ve got 3 GPSs.

Pamela: Well, the problem is your batteries…

Fraser: Yeah, what if it runs out? OK, so before there was GPS, navigators had to rely on the sun and the stars to find their way around the earth. It’s easier than it sounds if you’ve got the right instruments: clear skies, a really accurate clock and good books. So, let’s examine the history of celestial navigation, learn about the different methods, and we’ll give you some practical ways to go out and do this for yourself. Alright, so before we go into the actual navigation, I think it’s important to just talk about the geometry of the Earth and the stars and why this all works.

Pamela: Right, so we conveniently live on a rotating planet, and just like if you stand in one place on a floor with a tile ceiling, or on top of a tile floor — depending on whether you like to look up or look down — if you spin in one place, you’ll see that the object straight above you and straight beneath you stays perfectly stationary. You can do this in an office chair. It sometimes works better if you have someone else spin you, but not too fast because that’s a bad thing, but as you rotate, you’ll see all the other objects around you go on nice perfectly circular paths around you. Now, if for some reason, while you’re in your office chair that your companion is rotating for you, you lean back so that now you’re not looking straight up or straight down, but rather as you rotate, (and like you literally have to tilt the chair – don’t try this at home you will die) if you try tilting the entire thing, you can actually get it so that as you rotate, the point that you’re rotating about appears to be kind of off straight overhead, so you end up with “straight overhead” as this path where “straight overhead” stays at a constant angle. Now, that sounds confusing, but…

Fraser: No, I think I understand, but I’ll take a shot at it, too. Now, you take your chair, your office chair that you’re spinning around on and you put some kind of ramp underneath, so that the wheels of the chair are what’s on a slope, and so then the chair is still turning, but the point being that now your axis of rotation is pointed at a different spot on the ceiling, so it’s not just like you lean back on your chair while you’re turning because that’s just going to widen your circle. You’re still going to have the same axis of rotation. What’s important and what mimics what we have with the Earth is that you’ve got to have that angle away from straight up and down.

Pamela: And, if you measure the angle between straight overhead and that point that you’re rotating about — because you tilted your chair in a precarious and dangerous way (please don’t become an organ donor) — because of that tilt, you’re going to see that that straight overhead point, as it rotates past, always maintains the same angle off of that non-moving point that you’re rotating about.

Fraser: And now imagine that those flecks on the ceiling that you’re looking at are really stars.

Pamela: And so where I live, which isn’t too far off of 30 (I’m going to use 30 just because it’s a nice round number)…where I’m located, 30 degrees north of the equator (give or take a lot because I like round numbers) if I go outside at night, what I see is about 30 degrees above the southern horizon. I can look over and there’s Polaris, just hanging out fairly low in the sky, not very bright…this is one of those things that really screws people up. I think at least once a year I have someone go outside, look straight south at a planet and go, “Wow, look how bright the North Star is!” No, that’s Venus.

Fraser: Yeah, that’s only if you’re standing on the North Pole. So, once again, I think this is great because this is something even kids can do. If you know where the North Star is, go out some night with your protractor, and line it up perfectly, so you can measure the angle between the ground and up an imaginary line that goes up to Polaris, and that will tell you your latitude on the Earth.

Pamela: And it can be a whole lot simpler than using a protractor. One of the neat things about being human being is that we’re built to scale. So if I hold my fist out at arm’s length, the width of my hand at arm’s length is going to be 10 degrees. Now, little kids can have littler hands, but they’re also going to have much shorter arms; and conveniently, a little kid’s fist held out at arm’s length is going to be 10 degrees, and a giant basketball player with giant hands and really long arms — still 10 degrees. So one of the things you can do is just go out and “walk” your fists up the sky and prove, “Wow! OK, I’m 30 degrees north of the equator, and I see the North Pole Star 30 degrees above the horizon.”

Fraser: And I live near the 49th parallel; so for me, Polaris is 49 degrees above the horizon, and if you kept going north from where I live you would end up at the North Pole, and there it would be 90 degrees or directly overhead.

Pamela: And what’s nice about this is as long as you’re on one of the nice Atlantic trading routes, which is where all of the celestial navigation originally played such a strong role, Polaris just hangs out there being a nice let-me-tell-you-how-far-north-or-south-you-are kind of object. Now, the problem is as you start to get down toward the equatorial regions, well the Southern Hemisphere doesn’t exactly offer such a nice, polite star that is within a degree of the actual axis of rotation. So, instead what you have to do look at, well here’s a grouping of stars and within roughly the center of this grouping of stars is where the south celestial pole is located.

Fraser: Right. It’s not like we’re not thinking about you folks in the Southern Hemisphere. You just have a much harder job ahead of you. There’s the “Southern clump!” [laughing]

Pamela: [laughing] Right. So it’s a bit of a challenge. Now, if you happen to be exactly on the equator, you don’t really have anything to look at because the North Pole is buried in the haze in one direction, the South Pole is buried in the haze in the other direction; but conveniently, you can watch stars rise straight in the east, pass straight overhead and set straight in the west, and sort of go, “Oh, OK — I’m straight under the equator.” And as you get off a few degrees one way or the other you can look to see what is the path of the stars across the sky. It’s kind of annoying, but you can do it.

Fraser: So, then with celestial navigation, what was the historical way then that travelers used to use this geometry of the Earth and the stars to find their way?

Pamela: Well, the most simplistic way of doing it was simple dead reckoning. You figure out OK, there’s the North Star, or there is the “drinking gourd.” There’s actually a whole bunch of American slave songs that describe how to go north by following the constellations, and a whole lot of different constellations are made up to help reckoning direction based on the time of year. So, as you move from one culture to another throughout the globe, you find different constellations, and they’re like, “OK, look for this constellation – that’s North. Look for this constellation and that’s South.” Remember the time of year, and people would go “OK, I roughly know how fast I’m going. I know roughly what direction I’m going in,” and they dead reckoned. And this is the same thing you might do if you shut off all the lights in your house. You start off heading in a straight line down the hallway. You know it’s six steps to the bathroom, turn a sharp right, beware of the toilet, so you take one step to the left to step around it — you’re dead reckoning. Now, it’s one thing to do it in your house with the lights shut off trying not to wake up the dog or something, but it’s something else to be doing it at sea when the winds might be a bit higher, the tide’s a bit slower than you anticipated. So this wasn’t exactly the most accurate way to get from one point to another, but it’s the starting point that people had.

Fraser: Right, and so once again, for sailors, they use a terminology called “knots” and that’s a speed. And so you can know what speed you’ve been maintaining hour after hour after hour. You just add it up; you say, “I went seven knots in the last hour, and then I went 7 knots the hour before that, and so then you add it all up, and if you know that you’ve been keeping the North Star in a certain position in the sky, then you’ve been following a straight heading, and you’ve moved whatever a hundred knots in the last day.

Pamela: And if you think about it, Peter Pan is all about celestial navigation – the second star to the right…

Fraser: There we go! But this really breaks down because it stops you from going in circles, which is great, but there were a lot of mistakes… you don’t really know where you are on the Earth.

Pamela: Right, and this is where one of the problems we run into is, well the Earth is rotating, which means you have to know “when” you are to know “where” you are, and so you’re kind of good at noon. Figure out when is the sun at the highest point in the sky, measure how high it is above the horizon — that gives you north and south. You know what time it is, so you sort of get there — kind of, sort of, not great… With stars you look to figure out the rising and setting times, and figure out where you are north and south, and you can kind of figure out where you are, but again it’s all “kind of sort of,” so this is where the best way we ended up coming up with was actually initially what’s called an “intercept method” and this is where you figure out, “OK, where would I have to be on the planet to see the moon straight overhead? Well, I don’t see the moon straight over head, I see it X degrees above the horizon,” so draw a circle marking everywhere on the planet where you would see the moon that many degrees above the horizon. OK, rinse, repeat and do the same thing for the sun. You now have two circles and those two circles only have two possible solutions, two places where they overlap, and usually they’re separated by a few thousand miles, so you can figure out where you are by knowing within a thousand miles of where you are on the planet.

Fraser: But you need to have a sight line to both the moon and the sun.

Pamela: Right, so this doesn’t exactly work during new moon, it doesn’t exactly work during full moon, and it only works for part of the day the rest of the time.

Fraser: If there’s a delay, you’re going to get some inaccuracies because you check your moon sighting, and then you check your sun sighting 12 hours after.

Pamela: Right, and so that just leads to all kinds of hurt, but you really want to have both at the same time, so you’re kind of stuck for a large chunk of the month — well, at least a few days of the month — so that wasn’t the most accurate way of doing things, and this also is the problem of: you take your measurements, you go to your map, you draw lots of circles and you figure out where you were when you took your measurements. It doesn’t tell you where you are now, it tells you where you were.

Fraser: Right, and that’s not always so helpful, especially if you’re getting close to shore, there’s rocks, reefs…

Pamela: Right, so the next good method they came up with was what’s called the Lunar Distance — and none of these are actually good enough to tell you with reefs. All of these are going to tell you within 10 miles, 20 miles, 30 miles where you’re located. Most of them are actually 30 miles or more, which when you’re aiming for shore, that will get you to land unless it’s a really tiny island, but it’s not going to get you around that big coral reef – for that you’d need a map. So the next big improvement we came up with (and I was not alive when this happened) is a method that only works when the sun is down, and that’s Lunar Distances, and here you measure how far the sun is located from a key star or multiple key stars. And our moon is moving at a pretty good clip against the background stars. It moves about 12 degrees per day, and if you can make a very accurate distance determination of where the moon is relative to hopefully more than one really bright star, you can figure out, within about 30 miles, where you are on the planet.

Fraser: Because your view of the triangle — the angle of your view of the moon to that star — will change where you are on the Earth because the moon is much closer than those stars are.

Pamela: Well, that’s not the big thing. The big thing is you get the time from the measured angle between the lunar distance and the star, so you get the time from that distance and then you measure “Well, how high is the star above the horizon? How high is the moon above the horizon?”

Fraser: I see, I see, so in other words, when the moon makes that close approach to the star, it means that it’s a certain time with a high degree of accuracy. Throw out your clock. There’s your new clock.

Pamela: Yes, so you get your time and your position relative to the stars, based on the separation of the two objects, and then you get the “where” based on how high they are above the horizon.

Fraser: I’m not sure if we really explained this well, I mean, the fact is that if the earth didn’t rotate, if it just hung in space against the background stars, to find any place on Earth, all you would have to do is measure your angle to the North Star, or one star, and then measure your angle to another star, and then that would tell you your position on Earth – just like that — through triangulation, but because the Earth is rotating, it’s those stars you’re looking at to the west and the east that are just constantly changing, and that’s the real challenge that they’re looking to overcome. So, you’ve got like a new kind of clock, which is great!

Pamela: Yeah, so just to try to put it into a little more context, what you know is, “OK, so the moon and the star at a given time, according to a clock in Greenwich (this is how they did it – everything is measured off of Greenwich, England) at a given time relative to Greenwich, England have a given separation.” Well, no matter where you are on the planet, you’re going to see the same separation with the instruments they had. Now, what varies is how high in the horizon those objects are. If those objects were straight overhead in Greenwich at midnight, and you happen to be off the coast of California, you’re not going to see them, but if you see a time that corresponds to noon in Greenwich, but they’re straight overhead for you, you know that you’re 180 degrees around the planet from Greenwich. So you figure out what time do those two objects have that location, and where must the planet be rotated in order to see it, and that tells you where you are east-west, based on where the planet has to be to see a given alignment.

Fraser: And that is some wicked math.

Pamela: And this again gets you to the problem of “Oh, crud! First I have to measure the angle” – and the math is actually even worse than that because you have to correct for the atmosphere bending the light, so you have to correct for this atmospheric bending, and so first you go, you make your measurements, you then take into account atmospheric – the fancy word is “refraction” – you then do all of your calculations, and that tells you where you were when you made the calculations, and now you’re somewhere else.

Fraser: Right. So, if you’re coming up on that reef – not super helpful.

Pamela: Yeah, if you only know where you are within 30 miles, it doesn’t help you anyways with the reef, but if you’re finding a really tiny island, then you might care.

Fraser: So, what was the next real improvement then?

Pamela: We needed a watch. It’s just that simple.

Fraser: This is the problem, right? You had these clocks—these gigantic pendulum grandfather clock kind of contraptions. And you take one of those to sea… it’s not going to work because the rolling ocean is just going to mess up the clock, and within hours, days, minutes – it’s not going to be able to tell time. You need something really, really stable and really accurate and this just did not exist in anything you could transport with you.

Pamela: We just didn’t have the materials yet. We were still trying to figure out what are the different properties of the metals, how do we bond different metals to one another. Metallurgical science was in existence, but it wasn’t a detailed science yet, when they start worrying about this. So, in 1714, Great Britain put forward the “longitude prize.” It was established through the Longitude Act, and it was the British government’s way of saying, “Look guys, we really need to solve this problem. We’re kind of an empire at sea. Somebody, please go figure out how to measure longitude.” Different people took different methods of doing this, and actually the Lunar Distance method got 3000 pounds for making contributions that improved things. So Tobias Mayer got 3000 pounds from this prize for being able to figure out where you are within like 30 nautical miles – not great, but good, sort of, kind of…but the real trick came with John Harrison working to figure out chronometers, and this required new forms of steel to be made. It required figuring out how to build metals that didn’t require temperature corrections, and that’s one of the things that we take for granted. When you build a thermostat in house, it’s actually, well you probably don’t build it you just go buy it at Home Depot.

Fraser: I built mine.

Pamela: OK, fine. You can make these in a Physics lab class. You just get metal that on one side expands when it gets heated, and on the other side perhaps contracts – they just have different thermal properties that cause the little piece of metal inside your thermostat to change shape as the temperature in your house changes. It’s really amazing how much metals built with the correct properties will deform with even one or two degrees of temperature variation. Now, if you’re building a watch, you don’t want any thermal distortions going on with all the delicate gears and springs and everything else. So, we had to figure out how to make metals that, well, corrected themselves as needed as the temperatures varied, especially out at sea.

Fraser: Now, there’s actually a great show, I think it was called “Longitude,” that was done a few years ago, and they went into the whole history of the prize. It was a mini-series that documented it, and it was just fantastic.

Pamela: There’s a book as well. It’s by the same author that did Gallileo’s Daughter, Dava Sobel. I can’t recommend the books enough.

Fraser: I really liked the mini-series, too. So, I know he came up with a few solutions. He made these great big clocks trying to come up with a way to create a great big grandfather clock that could still withstand the rolling gait of the sea; but in the end, his final strategy was a pocket watch. It’s a big pocket watch, but it’s still a very pocket watch-y looking contraption, and it was a very accurate clock that you could carry around, and by carrying it around, you no longer need to worry about what’s happening with the ocean. It’s small and stable.

Pamela: What was quite amazing is that he tried his darnedest to get the prize money that was offered. It was basically a fortune by the standards of the time. It was 20,000 pounds if you could be accurate to within 30 nautical miles going back and forth and do it repetitively. Now, he showed that his instruments were only losing a handful of seconds on an entire trans-Atlantic journey, and managed to sail all the way to the Caribbean and then sail all the way back and the British Parliament said, “Oh, it was just dumb luck. It was a fluke. You have to replicate it.” So, they gave him some money – token money, no big deal — but really not enough, and so he, after much frustration, replicated the experiment and came out even better on the second try and the British Parliament said, “No, it’s still just luck,” and Harrison actually having to end up going to King George and get the King involved. Now, can you imagine? You’re a watchmaker, and you get so frustrated trying to collect the money that you know you earned building a watch, and no one really wants to help you and you have to go to the King and ask the King to intercede with Parliament, and Parliament still said “no.”

Fraser: And I know that with this device…Captain Cook considered it his most prized possession.

Pamela: Yes. James Cook had the very first one. He used it on his second and third voyages. He used the Lunar Distance model the first time. So he knew how to use the Lunar Distance method, which was then the best, and still swore by the chronometer, and King George III basically took one of them himself and kept it in the palace and found that it was accurate, that within a third of a second per day, and Parliament still said “no.” There was a lot of strange politics involved with this.

Fraser: Did he end up winning the prize?

Pamela: No one ever got the prize. They did end up eventually giving him the money, but not the prize. This is one of the frustrating things when you’re a scientist is there’s a lot of time it’s not the money you’re out for, it’s the name recognition. If you look at a lot of the [missing audio] prizes, the money that you have to invest to win the prize is much, much greater than what you win, but it’s being that person who won the prize – that’s where it is, and he died three years after they said, “No, but here we’ll give you some money anyway.” So he basically spent his entire adult life chasing a prize that bull-headed Parliament refused to give him.

Fraser: And so this methodology is essentially what is the modern celestial navigation. It’s the same system: you go out at night, you take your protractor…

Pamela: And it’s really a Sextant. You can build one of these with [missing audio]…

Fraser: You take your Sextant, you have a way to determine the angle, you point one part at the horizon, another part up at a star that you know what star it is, you mark down the time and the angle, and then you do another reading at another star, and then maybe if you want, another at another star, and then you look it all up in a table.

Pamela: Right. You figure out what time does that star have that angle above the horizon, and what’s often done, actually, is you figure out where the celestial meridian is, where is that line that goes from the north celestial pole down to the northern horizon and the southern horizon, and you look to figure out what time do stars cross the meridian. So rise times and meridian crossings are some of the most important times, and all of these times are tabulated. The U. S. Naval Observatory, in some ways, has a lot of the best catalogs because they’re necessary for navigation.

Fraser: And this is, I guess, where we wanted to turn this into “part-tutorial” anyway. We’re going to put a lot of these links in the show notes. There are both the books that you can look up the numbers, but also calculators on-line that you can just put in some of the data, and it will pop back out your location.

Pamela: And you can build very simple tools for the Lunar Distance method, or more accurate time plus angle. You need a Cross-staff and a Sextant. You can build both with paper, a protractor, straw, string and a meter stick, and you can watch the sky change.

Fraser: And you could use this method — there are still sailors now who don’t use GPS. They still will use the celestial navigation method to circumnavigate the Earth because it doesn’t matter if it gets wet — it still all just works fine. It doesn’t need batteries. It’s not as easy and simple a way, but you can definitely make your whole way around the Earth using just the celestial navigation.

Pamela: So, it’s all geometry in the end, and a few fairly simple tools, and it’s amazing what we’ve solved in the past 300 years.

Fraser: I’ve almost gotten interested enough to go and learn it… No, no, I’m still going to use my GPS.

Pamela: It’s still good…

Fraser: It’s still good… it’s very cool. Thanks a lot, Pamela.

Pamela: It’s my pleasure.

Shownotes

• The 88 Constellations — Universe Today’s Guide to Space
• FAQ’s on Constellations -- St. John’s U/College of St. Benedict
• Brief History of Astronomy — UC San Diego
• Asterisms (includes a list) — SEDS
• International Astronomical Union
• Eugene Delporte
• Henry Draper Catalogue — Wiki
• The Henry Draper Catalogue from SkyMap
• Zodiacal Constellations
• Early Chinese Astronomy — Ephemeris.com
• Astronomy in Ancient India – Ephemeris.com
• Sidereal Day — Universe Today
• Barnard’s Star — SolStation
• Star Wheel — Astronomy in Your Hands
• Sky & Telescope
• Astronomy Software:  The Sky
• Astronomy Software:  Stellarium (free)
• WorldWide Telescope (free)
• Book:  “The Stars:  A New Way to See Them” by H.A. Rey
• Quadrantids –Windows the the Universe

Transcript

Coming Soon!

Shownotes

Telescope & Accessories companies:

• Celestron Telescopes
• Orion
• Meade
• Bushnell
• Televue

Telescopes

• Refractor telescopes:  these are the least expensive, using refracting lenses housed in a long, thin tube mounted on a tripod.  Good for viewing the sun, Moon and planets where magnification detail is important but brightness is not.
• Reflector telescopes:  these telescopes are larger and use mirrors housed in large tubes; often reflector telescopes use a mount and are great for viewing faint, deep-sky objects like galaxies, star clusters and nebula.
• Compound telescopes:  also called cadioptric telescopes, use both refracting lenses and reflecting mirror in their design.
• Difference between reflector and refractor

Types of Telescopes

• Dobsonian Telescopes
• Schmidt Cassegrain Telescopes
• Newtonian Telescopes
• Ritchey-Chretien Telescopes
• Maksutov  Telescopes
• Binocular Telescopes

Accessories:

• Overview
• Drives
• Mounts
• Eyepieces

1. Nagler
2. Ethos

• Cameras
• Filters
• Anti-blooming filters
• Domes:

1. Astro-Domes
2. Ash Domes
3. Portable:  Shelter Systems

Share a telescope:

• Lightbuckets
• Slooh
• Rent-a-Scope
• Cherry Mountain Observatory

Transcript: Telescopes, the Next Level

Download the transcript

Fraser Cain: You’re drooling. I can hear you drooling over the telescopes. [Laughter]

Dr. Pamela Gay: I got sidetracked from pressing record by telescopes.

Fraser: We’ve explained again through astronomy and buy your first telescope. Now we’re going to take things to the next level and get you drooling about bigger and better telescopes. If you’re serious about astronomy what kinds of telescopes would give you the best bang for the big bucks?

When last we saw our telescopes we were trying to be as safe and inexpensive – big bang for the buck. We were suggesting the Galileoscope although we’ve had a bunch of feedback from people that Galileoscopes have been difficult to get with bad customer service.

Pamela: It’s not bad customer service; it is lack of venture capital.

Fraser: Lack of venture capital, lack of stock, lack of everything. The telescope itself is great if you can get your hands on one. That is the problem. Hopefully they’ll have that problem fixed in the next little while.

We’ve also recommended a nice 6-inch Dobsonian or a small inexpensive refractor, some binoculars, a planisphere, hit it with your eyeballs. Now we’re going to take things to the next level.

I think this show is going to be either for people who want to know how far this little hobby [laughter] can go or what will be the next level? If you do have a smaller telescope, you spent a few hundred dollars, you like it, you like that hobby and now you want to take things to the next level.

We’re going to talk about some of the technologies, some of the scopes and kind of push the limits of money and budget. Money is no object in this show. Alright [laughter] let’s draw a line here in the sand. What would you consider sort of a reasonable, inexpensive budget telescope? Where does that stop?

Pamela: There are people like me that anything that you can’t throw in a backpack or easily carry by yourself – that’s where you draw the line.

For me if I can carry it, that’s first tier. Second tier is a cement pier is required. Third tier is a “costs as much as my car”.

Fraser: Sure but you could have a portable telescope that costs thousands and thousands of dollars.

Pamela: Yeah and that’s where I sort of paused.

Fraser: We’re talking I’d say budget-wise?

Pamela: Budget-wise I’d say once you start getting into the multiple thousand dollars you have moved into a new range of commitment. Up to a thousand dollars, it’s a toy.

It’s a really nice toy; it’s an expensive toy but you’re still in the range of “I bought a laptop even though my company provides me one”. Once you start getting into the many thousands of dollars, you’ve changed your lifestyle to accommodate your hobby.

Fraser: You’ve chosen telescopes over trips; telescopes over new cars; telescopes over clothes. [Laughter]

Pamela: Yes, you’re going to work naked on foot because you have a really cool telescope.

Fraser: What are the kinds of structures? What kinds of telescopes exist as we move into those higher ranges?

Pamela: The first major investment that you start finding is the people who buy the twelve inch and the sixteen inch computer-driven telescopes and build some sort of a shelter around them and attach them to computers.

They make it so that you can no longer really look through them without doing surgery.

Fraser: Right but we’re talking about you might go and buy say a Celestron six inch telescope from them and you can cross into the multi-thousand just buying an eight inch, right?

Pamela: Right but you start asking what I can use this telescope to do.

Fraser: I guess the question is what the configuration is? What is the kind of technology that it is?

Pamela: That second tier of telescopes is when you’ve moved past your binoculars and you’ve moved past your Dobsonian telescope. This is where you start buying some sort of typically Cassegrain telescope.

A Schmidt-Cassegrain a Maksutov-Cassegrain are telescopes where the light comes in through the front of the telescope, reflects off of a mirror at the back of the telescope, hits another mirror at the front of the telescope.

The light then comes out through a small hole at the very back of the telescope and either comes into contact with eyepiece or for more serious observers comes into contact with some sort of a digital or film camera – mostly digital nowadays.

Fraser: When I mentioned Celestron, these are these snub-nosed telescopes, right? They look like they’re maybe 12 inches across or 16 inches but they’re also very short.

Pamela: Yes, they fold the light up. A good one is able to allow you to actually start counting the stars in the Milky Way. It will allow you to start seeing beyond the Seven Sisters and seeing dozens and dozens of stars in the Pleiades.

Fraser: Why is that better than the Dobsonian?

Pamela: There are two big differences that you’re dealing with. One is you have this snub-nosed telescope. One of the things that we talk about is the F-ratio. What is the fastness of an exposure time?

If you’re taking two different photos, one on a Newtonian telescope that has a longer focal ratio and one on one the little short-nosed Schmidt-Cassegrain telescopes, you can get the same image in much shorter amounts of time with these little snub-nosed telescopes.

The other thing that you’re dealing with is if you’re putting a really heavy camera on the side of a Dobsonian telescope it’s going to want to – under the force of gravity – tip over. You’re adding a lot of torque to this system.

It’s sort of like trying to hold a really heavy book bag with your arm held straight out from your side. It’s a lot of work. It puts stress on the system and starts to bend the system.

With the Schmidt-Cassegrain you instead have the camera at the very back end of the system. You can easily counterbalance it and you’re able to get much more study exposures without having everything twisted all over the place by the force of gravity.

Fraser: Okay, so then what is a Ritchie-Chretien?

Pamela: There are different types of optical systems that use different shapes of mirrors to get the light from the sky down into your camera system. With the Schmidt-Cassegrains you have two mirrors and a corrector lens. You get fairly large fields of view.

With the Ritchie-Chretien you have much smaller fields of view but you also have amazingly flat fields. What I mean by flat field here is the geometric distortions as you move away from the center of the image are very small.

If you were to take a piece of graph paper and image it with a Ritchie-Chretien all the little graph paper boxes would continue to look like squares whereas with other telescopes you start ending up with pincushion distortion and barrel distortion.

Because you don’t have a corrector plate with a Ritchie-Chretien you also have less light lost. Every time light interacts with the surface you lose some of the photons. They reflect off, they scatter off. They just don’t make it all the way down to your camera.

You have fewer surfaces with the Ritchie-Chretien. The reason every telescope isn’t a Ritchie-Chretien is the mirrors are actually really hard to make because they’re parabolic mirrors.

There’s a trade-off in difficulty in making compared to efficiency of the telescope itself. If you have the extra money, the Ritchie-Chretien is always the correct direction to go in my opinion.

Fraser: Then the last technology you mentioned was a Maksutov-Cassegrain [laughter]

Pamela: I’m willing to let you keep trying [laughter]

Fraser: No, your Russian is much better than mine.

Pamela: [Laughter] A Maksutov-Cassegrain telescope. It is very similar to a Schmidt-Cassegrain. It’s just slightly different geometries.

Most people when they’re switching back and forth between these two telescopes will never know the difference. The big difference is when you go from the Ritchie-Chretien to one of the different types of Cassegrain telescopes.

Fraser: I guess one of the other ways to go is just a gigantic Dobsonian telescope. There’s a guy on Hornby Island where I grew up and I was at his house a couple years ago and he has a 21-inch Dobsonian telescope.

It is 15-feet long and you stand on a big stepladder. It’s just a gigantic light bucket. Nothing fancy, no fancy optics, just a gigantic mirror that collects a ton of light.

The bigger your mirror gets the more expensive things get. That’s a way to have an enormous – but there’s no tracking system. If you wanted to look at a galaxy or whatever you had to push the telescope back and forth and lift it up and down to keep it in your field of view.

It was definitely no good for any kind of astrophotography or anything.

Pamela: This is where sometimes it’s not all about the size. It is actually sometimes all about the motors. When you start investing in these really amazing telescopes, there are two different ways to channel your investment. Actually, there are three different ways to channel your investment.

One of them is less useful than the other two. One thing you can do is just get bigger and bigger mirrors. The most cost-effective way to get giant mirrors is to get some of these giant Dobsonian telescopes like your —–11:11 telescope you got to look through.

Another route to go is to get a completely reasonable telescope; one with nice clean optics but nothing over the top. Invest in a really good camera and a really good drive amount.

If you have a rock-solidly mounted telescope, one that you have a small child bouncing up and down as much as their little heart can carry them and the telescope doesn’t move.

If you have that really good mount and a really good drive system on it so that you’re able to sit on one star for ten or twenty minutes without seeing any distortion of that star being round in your resulting images, you can do absolutely amazing things. For me the real direction to move in is to get one of these great drives.

Get a completely run-of-the-mill telescope system, a good solid camera on the back end of it – I particularly like the cameras because they make this very satisfying noise when they read out. It’s a silly reason to like an instrument, I realize that.

Apogee makes great systems as well; they just don’t make them using noises in the middle of the night. There are lots of different directions you can go and there are ameras as well.

Get a nice solid camera, a nice solid optical system and then pour every dime you have into a drive and nice solid steel or cement pier to put that drive on top of.

Fraser: What’s your favorite drive then?

Pamela: I love the Paramount’s, they just go. You can pile all sorts of different stuff onto them because it’s a very creative mounting system. They basically have a big old sheet of metal that you screw your telescope on to. It’s not sexy. It’s a gorgeous system, beautiful red design, lots of elegantly crafted surfaces to mount your telescopes on to.

It’s not what you expect when you think of big sexy observatory. You have plate of metal that you then bolt your telescopes on to. You can get three or four telescopes depending on their size side-by-side all looking at the sky where you can be looking with you eye through one, keep your tracking on.

You can have a tracking camera on one of them and have your big astrophotography camera on one of them. They track beautifully. They’re solid systems.

I’ve talked to people who have stuffed them in cars, lugged them all over the place setting them up and taking them down and they just go. You pay a small fortune for them.

Fraser: We’ll get to cost in a little while. Let’s not talk about that pesky money [laughter] for now. We’ll come back around to that. For now let’s just dream about the gear.

We’ve talked about some configurations of the telescopes, great big dog Dobsonian or a couple of the ways you can go with the Schmidt-Cassegrain. What about refractors?

Pamela: That’s part of the third option where when you’re making the next step. I wouldn’t go quite here yet. You can get absolutely pristine optics systems, gorgeous stunning chromatic refractors that make you feel like you’re flying through the universe as you skip from one object to another.

One of the amazing things with looking through a refractor is you have much higher contrast than you get with a reflecting telescope. That pays off. If you’re trying to do Astro-imaging you get really good results with the Schmidt-Cassegrain.

In my happy little dream world that I don’t live in but would love to, I have a nice Paramount on top of a cement pier someplace that doesn’t move and I have a good solid 16-inch Ritchie-Chrétien telescope mounted on that Paramount with an amazing Tele Vue Telescope as the finder scope. [Laughter] I can just sit and drink in the sky when I want to and also make amazing images when I want to.

Fraser: Right, your multi-thousand telescope just as your finder scope. Okay.

Pamela: Exactly. It’s my happy little dreamland that I don’t live in. I’m allowed to have whatever I want there.

Fraser: That’s what this show is all about. [Laughter] Dream big Pamela. I guess one other route you can go is really cool binoculars.

Pamela: Yes and what’s really cool is there are binocular telescopes out there. They’re really hard to look through if you’re an uncoordinated person like me. Imagine attaching to each eyeball a 15-inch telescope.

Fraser: I guess size-for-size binoculars are such a much better view. There’s just something so rich about seeing things that you just see details when you have both eyeballs going at the same time.

I forget the name of it – and you may notice this as well – if you look at some text across the room that you can’t quite make out with one eye and then switch to your other eye you can’t quite make it out. Yet if you open up both eyes and look at it you can read the text.

Pamela: What’s happening is your brain is basically folding these two images together the same way digitally you might combine two images. It is able to fill in information based on the two images they couldn’t fill in based on just one.

The human brain is an amazing device for co-adding images even though we don’t actually think that we’re doing that. There are defects in our vision. We have floaters. If you look through a pinhole at a really bright light you may be able to see junk floating around inside your eye.

These are dead cells – it is rather gross and we’ll not wander into biology right now. These floaters detract from your view of the sky. By having both eyes available your brain can go “oops, floater here, gonna subtract it and use the part of the image from this other eye over here”.

For reasons that I don’t think anyone can explain other than it’s the brain, when you look at the universe with two eyes instead of one your mind makes things three-dimensional. We aren’t able to get a separation between our two eyes to actually perceive a three-dimensional sky.

Our brain somehow fills in the pieces to give us a perspective that isn’t real but really cool to experience.

Fraser: Yeah and so does that kind of cover all of the high end gear? We’ve got…

Pamela: Giant binoculars.

Fraser: Big Schmidt-Cassegrain, you have giant binoculars. We’ve got really great refractors, super-duper mounts, monster Dobsonians; does that kind of cover the spectrum? Any other directions that a person might look at?

Pamela: I think that is indeed where you go when you’re planning and ready to move into the next level.

Fraser: Now let’s accessorize. [Laughter] We’ve already talked mounts. As you said a mount is half of the telescope. When you’re at that height, looking at that size of a telescope you really need a mount that is going to keep your image perfectly smooth, is going to track and is able to kinda crank that mass.

Pamela: And honestly it’s sometimes two or three times the price of your telescope.

Fraser: Yeah that’s the part that’s going to make people’s jaws drop. Actually I did an article for Wire about two years ago. I was interviewing all these astrophotographers and getting them to give me some prices.

That was it mount to X telescope X. They went on and on about the mount. But let’s accessorize. What about eyepieces?

Pamela: Yes. I hate this I suddenly have no memory for the new Tele Vue series. There’s the standard Nagler that everyone lives by. These are the types of eyepieces that anytime you see all the people who are in the know about eyepieces, their mouth drops open, saliva starts coming out – Naglers are awesome.

As near as I can tell Al Nagler is an optical genius. He has this new strain of eyepieces out that it feels like you’re looking at a hundred and something degree field of view. It’s just like standing out in the sky except you’re looking through eyepieces.

Fraser: Wow.

Pamela: It’s able to essentially, you look at the Pleiades and the Pleiades wrap around and fill your field of view. That’s just pretty amazing. In general everyone needs something of order of a twenty millimeter eyepiece, a forty millimeter eyepiece and if you have good skies, a six millimeter eyepiece.

The millimeter tells you how much magnification it is. Where a six millimeter is huge magnification and forty millimeter is bordering on binocular magnification.

The Tele Vue new series – it came back to me – is the Ethos series so you can basically see about a hundred degree field of view. They’re giant, they’re awesome. Look through one and dream along with us.

Fraser: Right when you say hundred degrees we’re talking about isn’t the moon a half a degree so you would be seeing a hundred moons?

Pamela: Yes imagine going outside and looking and seeing something the size of the Pleiades expanded out to fill that many times the moon across the sky. It’s taking and embedding you in the sky.

Fraser: Right – camera. If you get serious you’re going to want to install some kind of CCD camera on the back end.

Pamela: Right and if you’re doing astrophotography you probably want to get some sort of a high-end antiblooming CCD. This is one that when you look at too bright of an object doesn’t give you the criss-cross pattern.

If you’re doing science you want something that does bloom because you get better data even if you do when you make mistakes get to see them all over your image. A good high quality CCD, an SBIG, an Apogee, a Fingerlakes, any of these read the reviews.

There are some really nice ones out there. Personally I would never buy a color CCD because you get lower resolution when you do that. Get one that simply goes light – no light – and then buy yourself a filter set. Now we’re looking at eyepieces, camera, filter set on top of it.

Fraser: Filters – we haven’t talked about filters. Do you mean solar filters and different color filters?

Pamela: You can get solar filters and the color filters allow you to either make things look as they would appear to human vision. If you’re doing science you can get filters that are identical to the ones in the Sloan Digital Sky Survey or identical to the ones used in the Palomar Survey.

There are all sorts of different sets of filters out there. You can also get very narrow band ones that allow you to see specific oxygen lines, calcium lines and really figure out what is it that makes planetary nebula appear the way they do. What is it that makes star forming regions appear as they do simply by filtering down to certain colors of light that correspond to different atoms?

Fraser: Enclosures.

Pamela: Yes, [laughter] so the best enclosures are just plywood and hinges put together in the most creative ways. This is why I’m laughing. I’ve seen some of the most amazing enclosure that people have just designed to fit their own personal needs. Ones that fit only the observer they were designed to fit basically.

Fraser: Right.

Pamela: Just as you tailor a suit, you can tailor your observing dome to fit you and your chair and let all of you rotate little tiny circles as you look all over the sky. There are also great commercial domes out there.

There are things like the Robodomes for instance. All sorts of different ones – I don’t want to start endorsing domes because I personally a firm believer in Home Depot domes. Go buy plywood, build one around yourself, hope that you spouse comes out and lets you free occasionally.

Build something that fits you and your needs. If it’s just your telescope, basically build a box that flattens out when you want to observe and otherwise completely encloses your telescope. That way you get the best air circulation around your scope and you don’t care if you’re protecting yourself from the elements or not.

If you need to protect yourself then you start building a little bit more robustly.

Fraser: Let’s talk a bit about automation. We’re in the land of computers now so computers are guiding your telescopes. They are tracking.

If you’re doing your astrophotography they’re handling all your exposures. A lot of telescope work now is all being done remotely, even with hobby equipment.

Pamela: That’s right and one of the talks that made me giggle for the sheer joy of what the person had done was this wonderful talk at the American Association of Variable Star Observers.

This very mechanically inclined individual was talking about how he bought an old Queen Anne Victorian – which is what I have – and it needed a roof so he put a telescope in. [Laughter]

He rigged it up so that when it finished doing an observing run it would set off the alarm clock in his bedroom. He’d go down, go to sleep and either when a water sensor went off, or a weather sensor went off or when the observing run was done, it would wake him up and tell him “come do something with me now”.

Then there are also people with fully automated systems that are capable of detecting clouds for themselves. They go to bed having told their telescope: “take twenty of this, thirty of that call me in the morning”.

Their telescope is capable of waking up doing its standards, observing all over the sky, pointing itself, switching out filters, recognizing the conditions and then putting itself to bed in the morning.

Fraser: I’ve talked to amateur astronomers who do their observing from their laptop at their dining room table. They’re connected wirelessly out to the telescope.

Especially if they’re in the High Sierras and it is thirty degrees below zero outside and their telescope is in the most pristine viewing they can hope for they get to stay in the nice warm comforts of the home and their astronomy continues unabated.

Pamela: One of the really amazing things is there’s actually consortiums of amateurs who basically build their facilities at remote sites where there’s the resident of the communal property who is there in case something goes terribly wrong.

You pay him certain – basically the equivalent of your homeowner’s association – but this is your telescope observatorydom association who is out there in case something goes terribly wrong. But other than that, you might be in Indiana logging into New Mexico.

Fraser: You buy a great telescope. You rent space in this observatory as you said in New Mexico, and you control it entirely through the internet from your house.

You may spend months not seeing your telescope in person. Yet it’s your telescope and it’s doing what you want it to look at. Very cool.

Pamela: What’ really cool is – we say that too many times in this episode, I already have – [laughter] can you tell I like this subject? Not everyone can go out and dump $40,000 on buying a telescope. I’m happy my car works.

For people who need more economical options you can buy shares in professional grade telescopes across the planet. There are all sorts of different on-line communities of observers that jointly own networks of telescopes where people come in and it’s kind of like time-share vacation packages except you don’t end up randomly getting taken by strangers giving you free luggage.

These are actually useful time-shares where you have two or three hours a week, two or three hours a night that you’ve paid for. You get the telescope for you to use and you’re not responsible for the equipment.

You’re not responsible for site maintenance. Your fees go to cover all of that. All you have to worry about is “what am I going to look at tonight”?

Fraser: Alright so let’s bring this back now to Earth [laughter] and talk about money. So sixteen inch Schmidt-Cassegrain with a nice mount – what are we looking at there?

Pamela: The telescope with nothing else attached – we’re talking telescope, nothing, nothing else, you’re looking at several thousand dollars.

Fraser: Right, like two to four thousand dollars. This is your entry level nice telescope.

Pamela: Yeah.

Fraser: Then accessories, you’re easily $5,000 with everything.

Pamela: One really, really good eyepiece can cost you over $500.

Fraser: Then your sort of nice Ritchie-Chretien telescope? [Laughter]

Pamela: Nice Ritchie-Chretien, in my perfect little dream world that I will never live in – well I might – in my happy perfect little dream world, a ten inch Ritchie-Chretien costs $10,000.

Fraser: And that’s just a ten inch.

Pamela: Yes, that’s just a ten inch. For a sixteen inch we’re looking at over $40,000. For a twenty inch we’re talking $60,000.

Fraser: Some of the best amateur astrophotographers out there are using that. They’re using twelve to sixteen inch Ritchie-Chretiens.

It’s like a script you follow. Yeah so $30,000 or $60,000 additional accessories that’s sort of the world you’re living in.

Pamela: We haven’t even gotten to the mount which is about $14,500.

Fraser: Right a mount is another $15,000 on top of the $10,000 for your ten inch telescope.

In your entry level, really nice telescope you’re looking at about $25,000 just for telescope and mount and then another whatever, $5,000 for accessories. Not to mention your dome.

Pamela: One of those random figures that sociologists like to kick about because they collect numbers is someone who is serious about a hobby – whether it is scrap booking or telescopes – will over the course of their lifetime spend as much money on their hobby as they will spend on a really nice car.

It’s not unheard of to spend $30,000 on a really nice pickup truck if you’re an equestrian. Heck it’s not unheard of to spend that much on an SUV if you’re a soccer mom.

To then turn around and spend that much money on a hobby, if you have the land, the property, the skies fits with what sociologists say people do when they invest in a hobby.

Fraser: Okay so really if you were really serious, you’re looking at about $30,000 to $50,000 for a really good setup of a telescope.

Pamela: And other than the camera and you’re going to have to upgrade the engine now and then just like you have to tune up your car now and then.

Fraser: How much is a camera?

Pamela: The camera is probably going to be a couple thousand.

Fraser: Okay. So accessories, eyepieces, camera…

Pamela: But your eyepieces if maintained should last decades. Your telescope if maintained should last decades. Your mount is probably going to need its circuit board replaced at some point. It’s a circuit board – they go bad.

The telescope mount itself should again last a decade if not longer. Paramounts haven’t been around long enough for us to know what their life expectancy is. [Laughter]

But we’re looking at something where unlike other hobbies like I have to feed my horse every month. I will over the course of a lifetime spend this much money on my horse. I just spend a hundred dollars a month for the rest of my life.

Fraser: What about a big refractor?

Pamela: A really big refractor, really nice one you’re looking at $6,000 to $10,000.

Fraser: Then what about good binoculars? Double fifteen inch… [laughter]

Pamela: Double fifteen inch telescope.

Fraser: I would like to try that. I would love to give that a shot sometime. [Laughter] That would be neat.

Pamela: That’s a completely different range of concept. When you start looking at normal giant binoculars, you’re looking at a couple thousand dollars.

Fraser: Okay. So, Ritchie-Chretien is the high end. That’s where the big money gets spent.

Pamela: Yeah.

Fraser: Well, keep on drooling.

Pamela: Hey, Christmas is coming.

Fraser: Christmas is coming, yeah. I know what I’m going to give you. [Laughter] Yeah, next year, thanks Pamela.

This transcript is not an exact match to the audio file. It has been edited for clarity. Transcription and editing by Cindy Leonard.

Shownotes

Organizations to Check Out

• American Association of Variable Star Observers – do real science with variable stars of all types
• TransitSearch.org – help find transiting exoplanets
• GalaxyZoo.org – Humans can classify galaxies way better than computers ever could
• Seti@Home – put those unused computer cycles to work searching for alien life
• Sky & Telescope Magazine on observing meteor showers: when, where, how
• The American Meteor Society – where to report your meteor shower observations and turn it into useable data
• Heavens-Above.com – make sure your meteor isn’t actually a satellite
• The International Occultation Timing Association (IOTA) – help discover the shape of asteroids or mountains on the moon
• The International Dark-Sky Association (IDA) – track and combat light pollution
• GLOBE at Night – tracking light pollution by looking at Orion

Want more info on some of the science we talked about this week? Check out these old episodes (and their show notes) from our archive.

• Episode 2: In Search of Other Worlds
• Episode 14: We’re All Made of Supernovae
• Episode 22: Variable Stars
• Episode 30: The Sun, Spots and All
• Episode 36: Gamma-Ray Bursts
• Episode 37: Gravitational Lensing

Pamela’s Favourite Variable Star Observing Set-up

Telescope:
• Celestron – CPC 800 XLT GPS Telescope – 8″ SCT on GoTo Alt-Az Mount
• Meade – 8″ f/10 LX200R Advanced RC Telescope with UHTC

Camera:

• SBIG – ST-7XME Deluxe Class 1 NABG CCD Camera

Filters:

• Schüler 1.25″ UBVRI photometric/CCD imaging filters, set of 5

This transcript is not an exact match to the audio file. It has been edited for clarity.

Shownotes

Check out episode 7: Getting Started in Amateur Astronomy for tips and suggestions for the beginning amateur.

Basic Optics

• HyperPhysics Concept Maps: Light and Vision – links to lots of information
• Optical Aberrations

Binoculars

• Binocular FAQ
• Binocular Buying Guide
• Binoculars for astronomy and observing other things in the night sky

Telescopes

• Lens Combinations: Telescopes – includes interactive Java applet
• FAQ about Telescopes – Discovery Channel
• Basic Telescope Optics
• Optical Telescopes – from MSN Encarta
• Dobsonian Telescope
• History of the Ritchey-Chretien Cassegrain Reflector
• Schmidt-Cassegrain Telescopes
• Cassegrain Telescopes
• Schmidt-Cassegrain and Maksutov-Cassegrain Telescopes

Other Resources for Amateurs

• SkyTonight.com – Buyer’s Guide, reviews of equipment and lots of free observing tools including interactive star charts for all latitudes.
• NightWatch – an excellent book for amateurs anywhere, including starcharts good for Northern Hemisphere locations.

Pamela’s Dream System

• 19.75″ f/6.8 Carbon Truss Ritchey-Chretien Astrograph OTA – for personal imaging
• Paramount ME Robotic Mount
• Televue – TV76 – 3″ f/6.3 ED APO Refractor Package – For personal viewing (The first scope I am likely to buy, and the reason I don’t currently own a scope – I love this one too much to settle)

 

Transcript: Choosing and Using Astronomy Equipment

Download the transcript

Fraser Cain: This week we’re going to talk about amateur astronomy again, but this time we’re going to talk about the gear: how to choose it, fix it, upgrade it, buy it, where to buy it, how much to spend… all of that. Hopefully if you’re wondering what’s the best way to get rolling with buying your own telescope we’ll hash that out this week.
 
Before we talk about telescopes, let’s talk about some other stuff that you might want to get first.

Dr. Pamela Gay: Well I think everyone should start by going out and getting a planisphere or a star wheel. This simple little $5-$10 set of pieces of paper will allow you to find your way around the sky. It’s the stepping off point, the math that you can use to find “oh, that’s where Hercules is, that’s where Cassiopeia is” to find the constellations to then be able to say “oh, I know that Saturn is currently on the nose of Leo the Lion, I can find Saturn now.” They’re just wonderful, practical little devices that are adjustable so you can set them to the time of year that it is where you’re located and take off and explore.


Fraser: Everything with amateur astronomy is based on constellations. Everything that you’re going to want to see: nebulae, clusters, planets, binary stars, everything is like, “start in this constellation, look in this star of the constellation it should just be a finger width above it or three degrees below it.” So definitely learning the constellations is the first step and its amazing because once you start to know them, you walk outside, look up, and you’re like, “oh, there’s this and that” and it suddenly makes the sky very familiar. It’s not a haze of stars, it’s you know the constellations, you can orient yourself whenever you look up.

Pamela: I personally know the fall stars the best because that’s when I generally, for whatever reason, have gone camping. I’ve taken my planisphere and just learned what the sky looks like in September and October really well. But this time of year, I’m moderately hopeless. A planisphere is a small thing that I can just leave tucked in with my maps in my car and anytime I’m out doing a star party or I’m at a friend’s for a barbeque and they’re like, “hey, what’s that object?” I can pull out the planisphere and it’s right there. Plastered between a map of Chicago and a map of Boston I have a map of the Universe.

Fraser: (laughing) I like that.
 
So, to go along with a planisphere then, my recommendation is a good book that maybe has something you can fold out and has some sky charts in it that are maybe larger. The problem with the planisphere, I find, is they’re very small and its hard to put things into context while a book can be a little bit larger, you can lay it out flat, and you can have a bit better a view. My favourite book is NightWatch, by Terrence Dickenson, it’s spiral bound, you can open it up, it’s got one page per section of the sky and you can take your time to learn that.
 
I think the other thing you need is a red flashlight. They’re easy to find, cheap, and something that doesn’t ruin your night vision while you’re able to look at the sky map. Many of the sky maps are actually designed to be viewable with a red flashlight.


Pamela: And you want to use the red flashlight because it will help protect not only your night vision but the night vision of everyone around you. Our eyes are least sensitive to red light. So if I decide I’m going to flash Fraser in the face with a flashlight, and it’s a red light, his eyes will easily be able to go from staring at me being stupid to making out fairly faint objects in the sky.
 
If instead I beamed him with a blue flashlight, all the little chemical receptors in his eye that trigger on light are going to fire madly, and all those chemicals waiting to trigger are going to get used up and it’s going to take a while for those chemicals to build back up and for him to be sensitive to faint objects again.
 
So red lights protect your vision and the vision of those around you, and if you’re feeling really cheap, find someone’s red nail polish and just paint the front of a $2 dime-store flashlight.

Fraser: That works? Wow, okay. All right, so let’s talk about some actual gear. You know, you spend a couple nights looking at the stars, learning your constellations, time to use a piece of equipment. Let’s start with binoculars.

Pamela: Binoculars come in a bunch of different sizes. When you’re looking at the boxes they’re going to say things like 7×50, 8×25, 15×35. These numbers indicate the magnification of the binoculars as well as the size of the big objective lenses out at the front end of the binoculars (image right, 7×50 binoculars).


Fraser: So is it size in millimetres?

Pamela: Yes, it’s size in millimetres. So if you look at a pair of 7×35 binoculars, it’s going to be a magnification of 7 with 35mm or 3.5cm objective lenses.

Fraser: I can understand what the magnification is for: if it’s 8, it’s 8 times, if it’s 10, it’s 10 times, so if something looks like it’s a metre tall in the telescope it’s going to look bigger, right?

Pamela: Right

Fraser: By a factor of 10, right? But what does the measurement, the millimetres have to do with it?

Pamela: The size of the objective lens is going to tell you how much light is able to get into the binoculars and make it to your eye. The more light can get into the binoculars, the easier you’re going to be able to see really faint objects.
 
So these binoculars are taking and grabbing a section of the sky, a section of the light coming from distant stars and nebulas that is much greater than what you’re little tiny eyes on their own are capable of receiving. They’re then funnelling all of this light out through an exit pupil, out through the eyepiece that your eye can then receive. The more light the binoculars gather, the more light they can funnel into your eyes allowing you to see progressively fainter and fainter objects.

Fraser: So, I guess buying binoculars is a mix between those two numbers, right? What if you get something that’s really high power, like 20 power, but it’s maybe 35mm.

Pamela: The manufacturers of binoculars are actually pretty good with not wasting people’s time by combining huge magnification with little tiny objective lenses. So some common astronomy, giant objective lens binoculars are going to be a magnification of 11 with 80mm objectives, or a magnification of 20 with 80mm objectives.
 
The problem with these really big objective lenses is they start to get really heavy. So if you’re going to be out there holding them by hand and you’re just sort of interested in touring around the sky, I’d actually start off with something that has a 50mm objective lens and either a 7x or a 10x magnification.

Fraser: So you’re looking for a 10×50 or a 7×50?

Pamela: Yeah. We usually say 7 ‘by’ 50 or 10 ‘by’ 50.

Fraser: Right.


Pamela: These aren’t that heavy, you can hold them without big difficulties for 10-20 minutes, no big deal, and they’re going to allow you to see the nebulosity of the Orion nebula, to make out all the little stars in the Pleiades, to start to get at faint fuzzy objects like the globular cluster in the constellation Hercules.

Fraser: Right, or you could see Andromeda, the galaxy.

Pamela: You can see Andromeda – it actually goes straight across the field of view in many of these different pairs of binoculars.

Fraser: So chances are most people have 7×35′s kicking around; that’s kind of your common binocular. It’s the 7×50 or 10×50 that really kicks it up a notch.

Pamela: If you’re looking for binoculars for astronomy, you actually want to hold them out at an angle and see if they reflect up a purple-y colour at you. Really good astronomy binoculars are going to have a special coating on all of the surfaces that prevent light from getting reflected out of the binoculars.
 
Glass surfaces have this nasty tendency to not just transmit light, but to also reflect light. We’ve all seen this at night when we’re looking out of a bright room at a dark city. We can see ourselves reflected in the glass. That light isn’t making it through the window to the city (which may be a good thing). But if instead, you turn this picture around and you’re looking through a pair of binoculars at a bright star, you want all of the light from the star to get funnelled to your eyeballs and none of it to get reflected back out to your friend looking at you looking at something through binoculars.
 
This special, purpley-tinged over-coating can help make sure that more of the light gets to you than gets to people looking at the back end of your binoculars.

Fraser: So how much would you spend on a pair of binoculars?

Pamela: About 80 bucks.

Fraser: Right. So is there a tremendous difference? I’m sure if I look through some astronomy magazine, there’ll be binoculars there for $500. Is there a big difference between a pair of $80 binoculars and $20 binoculars?

Pamela: There can be fairly significant differences in how much they weigh, in the type of coatings that are used on the optics, but for someone just starting out, other than the difference in weight, you’re not going to notice any of these differences.
 
So if I’m buying binoculars to use with my students, I know those binoculars are going to have a shortened lifetime. Or if I’m just buying binoculars to keep poking around in my car where they’re only going to get pulled out now and then, I’m going to spend $80.
 
It’s only after I’ve completely fallen in love with using binoculars and I’m looking for something that I’m going to use night after night after night, that I’m going to invest larger dollars and get the several hundred dollar pair of binoculars.

Fraser: But definitely avoid those little tiny binoculars, the ones with the really small – like 7×20. It’s just not enough light.

Pamela: Right. 7×50, 10×50 – that’s what I’d start with.

Fraser: Let’s move on. So you’ve got binoculars – and that’s definitely what we both recommend, get a pair of binoculars first. One of the really nice things about them is you get that binocular vision – you can see with both eyes. There’s a certain richness to the three dimensions that you get when both eyes are working that you actually don’t get with a telescope.
 
Let’s talk about telescopes. Say a person wants to make the leap and buy a telescope. What’s involved in a telescope?

Pamela: For someone just starting off, you’re still finding your way around the sky, you perhaps don’t want to jump into a computerized this that and the other thing, you want to make observing a personal experience. For you, I’d recommend a Dobsonian telescope. These are often nicknamed light buckets.
 
They’re literally a giant tube that has a mirror on one end, the end closest to the ground, an eyepiece ¾ up the tube. Light goes in, reflects ¾ the way back up the tube, hits a tilted mirror and comes out to an eyepiece that is convenient for looking through for your standard, standing up adult.


 
They’re easy, easy, easy to use. There’s some new gadgets that make them actually great tools for learning the sky. You can get these encoders that you start off by turning everything on, and it will say, “point at” and it gives you some really, really bright star and you say, “okay, I’m there.” Then it tells you, “point at this other really, really bright star,” you point at that and it says, “okay, I now know what you’ve done setting up this telescope.”
 
After you’ve set it up, you tell it, “I want to look at this faint object I can’t see through my finding scope”. It will give you little arrows that say sway your telescope to the right, pull it up toward the centre of the sky, and it will help you find these fainter objects. You’re still looking at only spending a few hundred objects and you can open up all sorts of faint galaxies and really broaden your experience.

Fraser: What kind of sizes will these be?

Pamela: I’d actually recommend getting the largest telescope you can comfortably lift. For most people this is going to be a 6″ diameter mirror (see image right). Dobsonian telescopes also come in smaller sizes like 4″ and they grow all the way up to as much as 30″ or a metre in diameter.

Fraser: I actually used one last summer. Someone invited us to a star party and they had a 25″ in Dobsonian. It was 16 feet long, you had to use a stepladder to get up to the top and look through the eyepiece. So they get big.

Pamela: They’re absolutely amazing. I’ve seen some of the owners of these telescopes do the craziest things. They’ll be fine-guiding up at the top and decide “okay, I’m leaning over the ladder a little bit too much” and they’ll bunny-hop the ladder to get it closer to the telescope it’s the most insane thing I’ve ever seen, just done for the sheer pleasure of being able to observe better and for scaring all the amateurs around them.

Fraser: So 6″ Dobsonian telescope is good. And Dobsonian is named after the inventor, right? This is the one that’s sort of counter-balanced, it’s got a nice flat stand on it, looks like someone just took a tube and it’s sort of held and you can just move it around , it’s all manual, there’s no electronic gears or anything that goes on. You’re looking at a couple hundred dollars, right? $200, $250, not that expensive.

Pamela: It all depends what kind of size you’re going after. You can spend up to $500-$600 once you throw in things like a case, getting the encoders, and all that sort of stuff. But it’s still, given how much you can spend on a personal telescope, it’s not that great an expense.

Fraser: With a 6″ telescope what can we see?

Pamela: Here you’re going to start being able to see things like all the Messier objects, who will pop out of the sky at you. You’ll be able to chase M51, the Whirlpool Galaxy, you’re going to start being able to see the Lagoon Nebula, the Eagle Nebula. All of these objects are going to be opened up to you, and you might even start being able to see colour in these objects if you’re in really dark skies.

Fraser: You can see bands on Jupiter,

Pamela: Oh yeah.

Fraser: Saturn’s rings, Uranus, Neptune

Pamela: You can see the ice caps on the poles of Mars.

Fraser: Venus

Pamela: Has phases

Fraser: Yeah, that’s true. And the Moon is outstanding.

Pamela: Yes.

Fraser: The craters on the Moon, some of the amazing shapes, some of the walls and crater rims and seas… it’s quite something.

Pamela: And you can get filters for these telescopes that allow you to use them to safely look at the Sun. So you’re not limiting yourself just to night time observing. You can also get one of these filters and start observing our nearest star.

Fraser: So I think that definitely, with a 6″ telescope, knowledge of the sky, you’re able to move around, look at different objects, you can see with your own eyes pretty much every major thing that you’ll see pictures of from Hubble or those kinds of things.
 
But there are other different kinds of telescopes. You’ll see the one – I forget what it’s called, it’s a Meade one…

Pamela: One of Meade’s most popular telescope is the LX200 series. It’s a GO-TO telescope, they’re made out of Schmidt-Cassegrain optics which means you have a mirror that is as though you took a sphere of glass and cut off a section of it. They also have a glass corrector plate up at the front so when you go to look in the front tube of the telescope you see this glass plate. Embedded in the centre of the glass plate is a secondary mirror.


 
So the light goes through the corrector plate, hits the spherical mirror, goes up to the little mirror in the centre of that corrector plate and then goes out through a hole in the bottom of the mirror. You can then put an eyepiece, a camera, a CCD – anything you want, down below the bottom part of the telescope.
 
These are great telescopes if you’re starting to do astrophotography, if you want to start getting into imaging with all sorts of different types of digital cameras, and they’re good, rugged systems in general.

Fraser: And they’re easy to hold and carry because they’re much smaller, right?

Pamela: Yes, they have a very short focal length, so the distance between the front of the telescope tube and the back of the telescope tube is going to be much smaller.
 
Unfortunately with these telescopes you’re starting to add things like the corrector plate, the driver system. These systems often come with motorized drives that automatically track objects as they move across the sky. All these things are going to add weight, and time that it takes to set up the telescope. With a Dobsonian you just go out and plunk it on the ground.

Fraser: Right, but with the Dobsonian you’ve always got that problem of you point it at some object, especially with some higher magnification, tell your friends to come look and they say “I don’t see anything” and that’s because the rotation of the Earth has moved your field of view, so you’re always trying to put it back into view.

Pamela: You do a lot more babysitting with a Dobsonian.

Fraser: Yeah. And you don’t get that with one of these automated tracking ones.

Pamela: But the Dobs take no time to set up, whereas I have, on occasion where I was on an uneven surface and had a really cheap compass with me, spent an hour trying to get a Schmidt-Cass to work in a logical function.
 
So you’re going to add weight the system, you’re going to add set up time to the system, but the rewards you get are you can now mount a camera on your telescope and your telescope will now quite happily track objects across the sky.
 
The GO-TO systems on many of these telescopes will also allow you to just type in the name of the object that you’re interested in and it will automatically move the telescope to that object.

Fraser: I’ll be there’s controversy about that. I bet some people think, “in my day we chased down our nebula on our own we didn’t use some computer” but there’s something to be said for punching in numbers and having the telescope just move around and go “okay, here’s Saturn.” It can get pretty tiring, looking through the spotting scope, jiggling the telescope, looking through the spotting scope and trying to find the object. So once you’ve got a computer just tracking everything down for you so quickly, it’s a real pleasure.

Pamela: It really is, and it allows you to go after objects that don’t have any bright stars near them that you can star-hop to. It allows you to go after moving objects that you may not know exactly how to find three hours later because they’ve moved too far across the sky. The computers inside these telescopes can find things without having to star hop and can track fast moving objects if they have the correct software and it just opens up new parts of the sky that you couldn’t get to on your own.

Fraser: So how much are you looking at to buy one of these?

Pamela: Here you’re starting to look at $1000 up to tens of thousands of dollars depending on what system you go after and if you’re looking at something that will do decent astronomical imaging. You can get stuff under $1000 but it’s the type of stuff that might leave you less satisfied and less likely to use it.
 
One of the problems with a lot of these systems is a negative experience will cause you to leave your telescope in closets for years at a time. You pull it out, you call your friends over, you try to find some really cool, neat object in the sky, you can’t find it, you can’t get it set up, you spend forever trying to align it, nothing works, you don’t use it for 4 more years. Then your kid’s like “hey, there’s a telescope in your closet!” so you pull it out, the kid tries, fails and it goes back in the closet.
 
You don’t want to have that experience. Start with a Dob, and once you’ve sold yourself on buying a computerized telescope, buy the biggest aperture with the nicest mount you can get. A lot of people get cheap on how much money they spend on the mount, the part that holds the telescope up and steers it across the sky. The mount, in some ways, is the most important part because if it doesn’t work, the entire system stops functioning in a logical way and you’re lost among the stars.
 
So invest as much as you can, and you’re going to have a much better experience for it.

Fraser: Now, can we talk just for a second about what’s wrong with buying one of those cheap, $100 telescopes from Wal-Mart.

Pamela: Well… where to start…
 
A lot of them have really chincy drive systems, really chincy mount systems. So you’re out there, you’re slewing the telescope across the sky by hand and the whole system is wobbly. You look through it, you sneeze… the entire system starts oscillating and now you have Saturn bouncing left to right, left to right across your field of view. That’s not something that’s fun to look at unless you’re trying to get motion sick.

Fraser: And you have to over-correct, right? Where you know how much the mount will push back on you, so you move it beyond the field of view and then when you let go of the telescope it will sort of swing it back so that you are always having to over-compensate for the give in the mount. It drives me crazy.

Pamela: Yeah, it can get really annoying really fast, and again you have a negative experience, it goes and lives in the closet.

Fraser: What about the optics?

Pamela: The optics can be completely random. Sometimes you’re going to get lucky and get a telescope that happened to have come off the assembly line at the exact right moment of the exact right day of the week, and it’s perfect. But other times you’re going to get optics where everything that’s not in the very centre of the field is a little bit distorted. Where the shape of the objects in the field isn’t completely true, where things are either sort of tucked in towards the centre and the middle, sort of like a pin cushion shape, or they bulge out like a barrel shape. All these different aberrations can come in if someone hasn’t taken the time to very carefully check all of the optics before it gets shipped off to whoever you’re buying it from.

Fraser: But if you’ve already got one of those, you’ve already made that mistake, I think there’s something to be said for taking it out and having another go with looking around the sky. But there’s also something to be said for just saying, “don’t bother, buy a Dobsonian, you’re going to have a much more rewarding experience.”

Pamela: Honestly, one of the things I’ve done that’s made a lot of those cheap telescopes much more pleasant to use is I stick them on my camera tripod. I have a really heavy duty camera tripod. I can point all over the sky with it – it doesn’t track or do anything like that, but it’s stable. So if I find a ‘scope that has half-way reasonable optics and I just want to take a quick look at Saturn with a school-group that has a cheap school telescope, I bring my camera tripod and try it out and I usually get a much more positive experience.

Fraser: Yeah. Now, this is one of those dangerous hobbies where things get expensive. Where can this go on the high end?

Pamela: Ohh… you can easily spend $50-$60 thousand. One of the rules of thumb is if you have a hobby that you’re deeply invested in, the amount of money you spend on the equipment for the hobby is going to be roughly equal to the amount of money you spend on a car. So if you add up the cost of all your astronomy equipment (if you’re an astronomy freak) and you look at the price of your car, those two numbers are going to be roughly the same.
 
So, I happen to drive a beat up, used Jeep that I love dearly, and not own a telescope. I’m not quite sure what that says about me other than perhaps I’m still paying off student loans. But, the systems that I’d want, there’s this mount called a Paramount. It runs about $15,000 but that sucker will track anything and the pointing is perfect. You tell it “I want to look at the Red Spot” and it can centre to the level of looking at exactly the right spot on Jupiter. It has amazing pointing and you can stick big telescope tubes on it.
 
So you go out, and you buy the exact optical system you want, plunk it on and you’re off and running.
 
Of course, the optical tube I want is, again, in the tens of thousands. There’s a system called a Richey-Chretien. It’s not generally found at the low-end at all. They have mirrors that are hyperbolic in shape, which is very, very hard to make, which drives up the cost of the telescope. But they don’t have a corrector plate, so you have this great flow of air between the mirrors and that cuts down on thermal problems. You also have perfect seeing, a completely flat field of view. These are all a lot of technical terms… let’s just say, these telescopes make me very happy and make great images and this is the type of telescope that pretty much all professional telescopes are made.

Fraser: Let’s say you do have a telescope and you haven’t used it in a few years. What can you do to do some simple maintenance on it and get it back running?

Pamela: The best thing you can probably do is go out to your local astronomy club’s star party night with your telescope tucked under your arm and say, “here, can you help?”
 
You’re going want to do a couple of specific things. You’re going to want to collimate it, which is a way of aligning the optics. You’re going to want to learn how to align it on the north star and how to align your finding scope and your main telescope so you can use the finding scope to find things more easily.
 
So you want help collimating it, and you want someone to teach you those two different skills of aligning your telescope and aligning your telescope on the north star.

Fraser: So the collimating is turning those little screws that will be on the telescope to make it so the optics are all lined up properly.

Pamela: Right.

Fraser: That sounds like something that could go horribly bad.

Pamela: It can go horribly bad, which is why I say go find someone to show you. There are all sorts of websites that will walk you through all of the steps, but sometimes it’s just nice to have a mentor there to help you.

Fraser: I guess it’s just like tuning a piano.

Pamela: Exactly. If you tune it a little bit wrong, you can actually do permanent damage, but that usually involves turning a screw hard enough that you know you’re doing something wrong.

Fraser: What about cleaning it? I’m sure the glass can get scratched…

Pamela: The way optics are cleaned at a lot of professional observatories is with ethel alchohol. It evaporates off clean, and if you have something that’s kind of stuck on, human breath works wonders. You just sort of go “hhhh” (Pamela breathes onto her mic). Do that, steam up your optics, and there’s special optical tissues that you can buy – they’ll have them at photo stores – and you can use those as well as camel brushes to get off any chunks that had the misfortune of landing on your optical system.

Fraser: But definitely don’t use cotton or toilet paper or

Pamela: Don’t use your shirt, don’t use paper towels, don’t use toilet paper… all these things are going to ruin your optics. Whatever you do, don’t use Windex.

Fraser: Yeah, they’ll have little pieces of them that’ll scratch. Great.
 
I think this is one of those episodes where we want to hear your stories. Let us know how it went. Did you get some gear? Did this encourage you to go out and take your binoculars out… let us know what happened. We’d love to hear from you.

Pamela: So enjoy the sky. There’s lots of neat ways to enjoy it, either naked-eye or with really expensive telescope systems. Find what makes you happiest and go for it.

This transcript is not an exact match to the audio file. It has been edited for clarity.
Images provided courtesy Oceanside Photo and Telescope