I had clear skies again last night, and I remembered to look for the Moon while it was slightly higher in the sky. I set my telescope up on the front porch shortly after sunset. The Moon presented an incandescent, imperceptibly fuller crescent facing the failing twilight.
Because it was higher, I had a better perspective, I had more time to take photos, I had more time to check my settings, and my photos had less atmosphere through which to photograph (meaning less distortion). And because the crescent was fuller, I captured more detail in my photos.
I always remember to spell out acquisition details in my astrophotography posts, but I’ve found instead people most often ask what equipment I use. I usually don’t list this in detail, both because I’ve usually already mentioned my equipment in earlier posts and also because I find that the exact equipment I used on a given night is partially convenience and whim, not meriting any particular recommendation or endorsement. My photos are within reach of all sorts of equipment of various kinds and prices, given practice and technique, and the last thing I want to do is give someone the impression they need to spend over a thousand dollars to do what a two-hundred-dollar telescope and a smartphone can do.
However, I’m going to try to make an effort to name what equipment I use now and in the future just because it’s so commonly asked. Maybe I’ll need to reference it myself in the future, too. So last night, I used
Those are the only four pieces of hardware I used last night.
I aligned the telescope on the Moon, which let it track roughly. This meant it needed periodic corrections to keep it from drifting out of view (once every several minutes). I concentrated on keeping the extents of the arc within the viewfinder.
Once it was centered and roughly focused, I used a feature on my camera called the “Focus Magnifier” to fine-tune the focus. I’ve found this to be indispensable. Using this feature, I zoom in to a close up view of some section of what the camera sensor is seeing. This way, I can make fine adjustments to the telescope’s focus until I get the best possible clarity available. I can also get a good idea what kind of seeing I’ll encounter that night—whether the sky will shimmer a lot or remain still. I was lucky last night to find good focus and good seeing.
Once focus is good, it can be left alone. I ensure that the adapter is locked tightly in place so that nothing moves or settles, keeping the focal point cleanly locked on infinity.
Then I turned the ISO up—doubled it. The Moon is a bright object, so I was not keen to use something I would use for a dark site, but I settled on ISO 1600. My goal was to reach a shutter speed of 1/100 seconds, which I did, without losing the picture to noise or dimness. A higher ISO works great at a dark site, but the Moon is quite dynamic, so I felt like I had less headroom. In any case, I used 1/100 seconds’ exposure and ISO 1600 for all my photos.
I captured a short 4K video before I began so I could capture the seeing conditions that night. I recommend viewing it fullscreen, or it will look like a still photo—the sky was placid as a pond last night.
After taking the video, I realigned the telescope slightly and, using my remote controller so that I could quickly actuate it without shaking the telescope, I took 319 photos, occasionally realigning to correct for drift.
Unfortunately, Venus and Mercury had already sunk too low to get a glimpse, so I packed it up and went inside.
I moved all the photos, in RAW format, to my computer from the camera. Then I converted them all to TIFF format. These two steps took probably something like an hour and resulted in seven and a half gigabytes of data.
Because the Moon drifted, due to the rough tracking, the photos needed to be pre-aligned. I used a piece of software called PIPP for that. Without this pre-alignment step, the tracking and alignment built into my stacking software struggled mightily with the photos and created a mess.
Its output was another series of TIFF photos. I found afterwards that two of the photos were significantly too exposed, leaving many details blown out, so I excluded them from the rest of the process, leaving me with 317 photos.
I opened these 317 photos in AutoStakkert!3 beta. After initial quality analysis, I used the program to align and stack the best 50% of the images (by its determination). This took a bit less than ten minutes and left me with a single TIFF photo as output.
Image stacking leaves behind an intermediate product when it’s complete, which is what this TIFF photo is. It’s blurry, containing an average of all the 157 photos which were composited into it. However, the blurs in this photo can be mathematically refined more easily using special filters. I used a program called Astra Image to apply this further processing. In particular, I used a feature it calls “wavelet sharpening” (which can be found in other programs) to reduce the blurring. I also applied an unsharp mask and de-noising.
Finally, I used Apple Photos to flip the resulting photo vertically (to undo the inversion which the telescope causes) and tweak the contrast and colors.
Click to view the photo in fullscreen if you can. There’s a lot of detail. The terminator of the lunar surface stops just short of the Mare Crisium (the Sea of Crises), the round, smooth basalt surface right about the middle of the crescent.
I can’t help but compare this one to the photo from the night before: what a difference a day makes. I had more time to work, more photos to take, and the benefit of yesterday’s experience to help improve.
Now it’s clouded over here again—Portland weather—and I can’t practice anymore for a while.
It’s been over a year since I wrote my first post in this series, Beginning Astrophotography: Jupiter Ascending. I’ve learned a great deal about what’s possible with the equipment I have on hand and what it takes to acquire a photograph like the one I took of Jupiter this May, with which I’ve begun this post. It represents both a rare night of luck but also a couple of years of practice and reading.
This post is going to be a long one, with lots of sections, each describing a piece of my journey toward grabbing that photo. In my previous posts, I’ve withheld a lot of detail in order to focus on my personal story. My audience has consisted of my friends with whom I want to share my enthusiasm, whether or not they care about the practicalities.
Now I want to circle back and fill in those gaps. In this post, along with the story, I’m intentionally targeting an audience interested in the marrow of astrophotography, with its attendant detail.
I am an amateur, pursuing astronomy as a hobby in my free time, as I have done for less than two years now. What I describe below, I hope, lies within the reach of motivated hobbyists who may be fortunate enough to find themselves with the time, money, and circumstances to support the pursuit for themselves.
In my earlier post, I discussed equipment choice a bit. Now I want to talk more about why I have the equipment I have, what its capabilities are, and what its limits are.
When I think of hobbies, I think of, say, knitting, drawing, fishing, hiking, or building things out of matchsticks. Each of these hobbies lets you start off with a handful of dollars, a few odds and ends lying around the house, or a castoff from a friend. What you get out of each depends a great deal on the effort and practice you put in up front. If you want to spend hundreds or thousands later on, that’s fine, but your results won’t commensurately improve without that effort first.
Then, I’ve found there’s a whole world of hobbies that are rather pay-to-play—photography, for example. You save up for that first camera, and maybe it comes with a lens, but gosh, the result leaves something to be desired. You need another lens. But this one won’t zoom in! Before you know it, you’re a handful of lenses deep and realize that you need a camera bag. Now you’re realizing your new camera takes photos faster than the SD card can save them, so you need a new one of those, and you might as well have a spare. And so on.
Astronomy as a hobby can go this way. Once you’ve got an entry-level telescope, you might be set, but then you might begin to see its shortcomings. Last year, I found myself at this point, considering my first upgrades. I feel extremely lucky that, at this point in my life, I can indulge in one of these pay-to-play hobbies.
Combining photography with astronomy just multiplies the effect. I began with a really modest budget, and then I leapt in with both feet.
The first budget I set for myself was about $300, but I ended up stretching to about $400. I chose a budget small enough that if I had a bad experience, I could eat the cost without too much pain. If I had it to do again, I might have set a budget closer to $200, and I would have come out of the experience just as informed and enriched.
I had had no intention of doing any photography yet because I had literally no idea it was possible, what equipment was necessary, or how hard it would be. I figured it was out of reach, so I ignored it as a consideration.
With astrophotography out of the picture, I only considered what would give me the best view for my dollar. I began trying to search for how magnification worked until I learned that magnification was practically limited by other factors, like eyepiece choice, focal length, and aperture. In fact, the more I read, the more aperture stood out as the one most salient attribute of a telescope’s viewing ability.
I also explored a maze of other features, like fancy, computerized controls and such, but I found those dug significantly into the price. When telescopes in my price range included fancy features, they also invariably had smaller apertures.
So I had to trade off between fancy features and sheer viewing power. I decided to prioritize for aperture. I didn’t know what I’d be looking at, so I thought having as much aperture as I could afford would accommodate the most situations. And I thought the fancy features would be intimidating and hinder me from learning the mechanics of using a telescope.
I ended up buying an eight-inch reflector. It cost me $380. Reflectors use an extremely simple design—I was paying for little more than a metal tube and a couple of mirrors. If I had known I’d be primarily looking at bright targets (moon and planets), I might have made a different choice and not prioritized aperture as much. In fact, the telescope I got was right at the edge of what I could carry in my car or by hand.
I had tried to take a picture of Saturn that first night, but I didn’t get anything recognizable. It didn’t take long for me to decide both that, yes, I definitely wanted to pursue this hobby further, and I definitely wanted to share it with others who couldn’t be there with me.
As I’ve mentioned, I feel I’ve had a lot of personal luck in being able to set a much larger budget for my second telescope. I believe that I budgeted around $3,000, but in the end, I’ve probably invested, all told, $4,500 in it and accessories. Not all of that has been spent at once, though. In fact, again, some of it was possibly overspent since I didn’t know exactly what I needed.
In fact, I felt comfortable with a larger budget because I had decided I was investing for the longer term—I do not intend to buy another telescope for a very long time, if ever again. So I thought of this as my “lifetime” telescope.
In buying the second telescope, I wanted a more compact tube (in length), mistakenly thinking it would mean a lighter overall telescope. I was dreadfully wrong—the current telescope altogether weighs something like a hundred pounds assembled. I also thought it would be more portable, but again, I was wrong—a more complicated setup has led to many more (heavy) pieces to set up and break down each time I want to use it.
I continued to focus on aperture (forgive the pun), but I also wanted computerized tracking, a hard requirement for more serious astrophotography. Computerized tracking lets the telescope follow an object in the sky as it moves—as the Earth moves—so that the object doesn’t slide out of view or move around.
In my budget, my requirements meant buying a Schmidt–Cassegrain telescope kit, including a computerized mount. A Schmidt–Cassegrain telescope (SCT) is a kind of compact reflector telescope combined with a special lens, called a corrector plate.
I was daunted by the prospect of learning to put it together and break it back down—each time I wanted to use it. I was daunted by the prospect of figuring out how to align it to the sky—each time I so much as moved it a few inches. I’ve gotten better at these things over time, and they’re not so bad, but if I had begun with this telescope, I might have literally cried and given up at some point. Learning to use it has been, in itself, a journey for another time.
I also got a few accessories to go with this telescope, too, including a camera adapter. (I’ll mention other accessories as they’re relevant.)
Camera and Adapter
I already owned a camera for taking photos, and I needed to figure out how to connect this thing, somehow, to the telescope. It turns out that adapters exist that lock onto the camera body like a lens would, while the other end is shaped like an eyepiece that goes into the telescope. They do nothing more particularly special than hold the camera’s sensor at a fixed position and distance from the telescope’s back opening (or an eyepiece, if one’s in there). From there, you focus the telescope’s light onto the sensor, and the entire telescope functions as one giant lens for your camera.
As I mentioned in my FAQ, it’s even possible with some practice simply to hold any camera up (with a lens) to the eyepiece of a telescope, focus, and take a photo. This works, even with a smartphone. There exist adapters to help with this.
My camera is a Sony α6300 with an APS-C CMOS sensor. It’s a mirrorless camera, making it like a smaller version of a DSLR camera. I chose it for more general photography, but it works decently for astrophotography because it’s light and takes 4K-quality video.
I live in the Pacific Northwest, where conditions usually aren’t conductive to astronomical observation in the first place. Even when the sky clears, that isn’t the end of the story. For planetary viewing, astronomical seeing plays a huge role. Without good seeing, Jupiter’s disc appears to smear and soften randomly, no matter what I do or how hard I try to focus. Magnifying more closely doesn’t matter; it doesn’t help.
Below, I’ve added a small video clip of what Jupiter looks like under relatively poor seeing. It wobbles, shimmers, and smears.
Seeing changes from moment to moment, so maybe if you’re patient, the seeing will clear for a moment on a given night, and you can take good photos or video. The problem is, without good conditions to start with, it’s tough to know if you’ve focused properly in the first place.
Another problem is that observing Jupiter actually requires some study and practice, to become accustomed to its appearance through the telescope: how it should look when it’s perfectly in focus, what distortions come from bad seeing, and what distortions come from bad focus.
Last year, I used a lot of trial and error. I found that each night I got a little better, saw a little more detail. Where first I saw a mottled disc, I wondered later, were those cloud bands? Was that the spot? Is that how it really looks, pale and pink, instead of blood red like I’ve seen on TV?
I learned to use the moons, which appear to be much smaller and nearly points, to improve my focus. I also tried using a device called a Bahtinov mask, which is a simple piece of plastic with slots that goes over the end of the telescope. Its job is to distort point sources of light in a specific way such that, when something’s slightly out of focus, it’s more obvious.
See the two examples below. The first is slightly out of focus, while the second is perfectly in focus.
Both photos look almost identical, but look closely. The diffraction spikes (the lines of light) don’t quite meet in the center in the first image. In the second one, they do. The smaller star off to the left looks a bit softer in the first photo, while it looks sharper in the second. The difference is subtle, but it makes a world of difference—literally.
Since the whole sky is at the same focal distance, I can use the Bahtinov mask to improve my focus on a small point source of light, and then I can home in on Jupiter. Since I know it’s precisely focused at that point, I know any additional distortion is due to other factors, such as the atmosphere.
Now, assuming that I have a night of clear conditions and decent seeing, I’m still limited in the detail I can observe in any instant. At right, I’ve added an image of an individual frame from a video of Jupiter I took the night of 3 May 2017. It has not been altered in any way, except that it’s been cropped and rotated. The exposure length was (if I recall correctly) one eightieth of a second.
It was chosen from among thousands as representing one of the very best possible frames I took. The Great Red Spot is clearly visible in the lower left quadrant. There are distinguishable cloud bands, but their finer details are not present; they appear to be even, smeared stripes across the surface.
This is as far as I’ve ever gotten with an individual photo. I have literally hundreds of similar photos, all taken under slightly different circumstances and with slightly different methods, but they all end up looking roughly like that one. More detail eludes me, at least on a sensor.
(With the bare eye, a little more detail is to be found. The eye can see things the sensor can’t, and I can use nice eyepieces that aren’t compatible with my camera.)
I know I can buy yet more stuff and get more detail. It’s out there. I’m only a couple of years into my hobby here, and I haven’t explored CCD sensors or apochromatic refractors, and I’ve barely begun to learn to get all the detail I can from the photos I have taken. But this is the place I’m stuck at now.
So, if computers didn’t exist? The story would end here. But again, I count myself lucky.
Computers have brought lucky imaging within the reach of amateurs like me. Specifically, I’ve been practicing a technique called image stacking. The idea is that, with some software I can find online, I can take lots of individual photos and combine them into a single better photo. That’s how I created the photo of Jupiter at the top of this post, along with the one below.
Instead of just taking hundreds and hundreds of photos, my feeling is, it’s easier just to take a video over several minutes. Here’s where the benefit of 4K video really comes into play. By taking a video over several minutes, also, I increase the odds of encountering a few moments of exceptional seeing. I can even fool around with the focus during the video, sacrificing some frames as “first pancakes” while I get things right. The software later can identify the best frames and use those.
With Jupiter, I can’t video too long, though. Jupiter makes a full rotation inside of ten hours. This means that its features will move across its surface and blur an exposure over the course of some minutes, even visibly from Earth! To play it safe, I try not to use frames across a time period wider than about a minute or two. (A lot of software comes with a “de-rotation” feature for this reason, but it’s better to avoid it in the first place.)
The software I’ve found online so far is pretty daunting, confusing, and flaky. Most of it only works in Windows. I’ll describe here what I do, but I strongly encourage you to find what works for you because I am pretty sure I am doing something wrong or sub-optimally. I only hit upon this workflow after trying many, many different things over several nights and weekends, until the end result was somewhat presentable.
The first thing I do is take the video file I’ve imported off my camera after observing and load it into a piece of software I found called PIPP. Its job is to take the video, crop it down, rotate it, find the best frames, extract those, put them in order, and output them.
It took a lot of trial and error to get some output that worked, and I’m still not sure I’ve done it right. Problem is that with a video of any size, it takes most of an hour to do its job, so I usually make my best guess and look at what it outputs to see if it’s reasonable.
From a video of several thousand frames, I usually cull off about 1,200 of the best frames (as PIPP determines them).
Once those 1,200 frames are sitting in a folder, I’ve been using a piece of software called RegiStax to turn them into a single detailed image.
I’ve added some screenshots above of RegiStax, as I’ve used it to prepare an image of Jupiter from frames similar to the one I included above. My experience of using this software is that it’s extremely confusing and took many hours of practice to get to work. Making things worse is the fact that any misstep would cause the software to misbehave or outright crash, so I became accustomed to simply closing and reopening RegiStax—and starting from scratch—anytime I did something wrong.
Finally, compounding the whole unpleasantness, I couldn’t see whether my result would turn out worthwhile until the very end when I began applying wavelet filters. I found myself flying blind, from beginning to end, until a planet popped out, usually wasting an hour each time.
As near as I can tell, though, here’s roughly the process from RegiStax, though.
Hit “Select” in the upper left and open up all the images to stack at once.
At this point, you’re looking at the “Align” tab, and you’re expected to align the images. (Nothing tells you this. You’re expected to have read it on the site.)
First, hit the “Set alignpoints” button. (I found that I had to tweak the alignpoint parameters to allow a few more alignpoints. It took me hours to figure this out.) This happens quickly and automatically.
Then click “Align”. This takes a moment.
Finally, hit “Limit”. I found through trial and error that a smaller limit was better in my case, likely because my photos were somewhat less detailed. I ended up limiting down to something like 20% to 40% of frames.
At this point, the software automatically moves you over to the “Stack” tab. I mostly left what I saw alone and hit the “Stack” button. This takes a moment. The image looks strangely blurry after this.
Finally, I found myself at the “Wavelet” tab. I had no idea whatsoever what to do here, so I searched online for things to try. I’ll relate what worked for me (specifically, what I changed from the default).
I used the dyadic instead of linear scheme.
I used the Gaussian instead of the default filter.
I believe I linked the wavelets, but I only dimly recall.
The first wavelet filter I used aggressively, with denoise set to 0.11 and desharpen set to 0.125 or so. These values can be tweaked. Then I moved the slider to the left, and this is when I finally saw some detail emerge.
The second wavelet filter I slid without changing any values.
I tried adjusting the sixth filter very slightly, but its changes were extremely aggressive.
The wavelet filters add some aggressive artifacts which I compensated for by clicking the button on the right called “Denoise/Deringing” and used some of its sliders slightly until the ring artifacts softened.
Once all that was done, I saved the resulting image, the one I began this post with. I also tried this with a second video and had similar (but slightly less impressive) results. The original video was slightly differently taken, and some of the processing I used was also slightly different.
These photos represent the very best I’ve ever managed to take of any celestial object so far. Finer details are visible, such as some finer cloud bands, and a hint of the small white clouds between the Great Red Spot and its adjacent cloud band.
Lucky Stars (and Asterisks)
I’ve learned a lot along the way, and having done so, I can usually process a video of Jupiter in about an hour into something clearer. There’s a ton of room for improvement. RegiStax is literally just the first piece of software I managed to figure out enough to get any kind of result. There are probably better processes, better pieces of software. And there are definitely better pieces of hardware, better photographic and noise reduction techniques.
I’ll update this post with clarifications and additional information as needed. Feel free to contact me (especially on Twitter) to let me know what I can improve. Thanks so much for reading about what has been a labor of love for me.
When I mentioned I was writing another post about astrophotography, I also asked if there were any questions I should make sure I answer.
I’m very grateful especially to Julia Evans for asking several very good ones! A lot of these questions have come up more than once, so I thought they deserve their own post. I’ll answer these below to the best of my ability.
My answers are all based on my own experiences and limited by my own knowledge, of course. Many answers will vary based on the experience and equipment of the observer, too. I will try to address this in each answer.
Can I do astrophotography in my city?
There are certain kinds of astrophotography which are relatively easy to do within a city, and some other kinds are rather difficult. It depends a great deal on the subject you choose, the equipment you have, and where your city is located.
The biggest challenge to pursuing astrophotography in a city is light pollution. (Aside from this, cities also obstruct the sky with its buildings and other structures.) But it isn’t hopeless! Bright objects are still visible. Think about how Venus remains visible even at dusk when the sky isn’t even fully dark yet!
Depending on where you are, various objects may or may not be visible. A good way to get a sense of what’s visible with the naked eye or with a telescope is by using the Bortle scale. From there, you can try to identify which zone you’re in using a map such as the light pollution map at the DarkSiteFinder. See the screenshot of what the area of northwestern Oregon and southwestern Washington looks like.
The planets are so bright, it won’t matter where you are: light won’t drown those out. Likewise for the moon. Through a telescope, bright star clusters and nebulae would remain visible as well, and you can sometimes squint and see those even without. I’ve also seen decent photos of some very bright nebulae (like the one in Orion) from inside cities.
Other subjects, like wide-field views of the stars, details of dusty or dark nebulae, and faint galaxies will be very challenging to photograph. The kinds of exposures needed to capture these will also capture lots of incidental light.
A telescope’s primary job is not magnification but light-gathering. The bigger the telescope, the more light it gathers. It’s the same way a magnifying glass can turn sunlight into a spot hot enough to start a fire. A telescope will make any light in the sky much brighter. In the city, it unfortunately can capture a lot of light you don’t want to see, and details will look pale and indistinct.
How fancy does my equipment need to be?
Just like with any photography, there’s a huge range in fanciness, costing anywhere from a couple hundred dollars to many, many thousands.
A beginner’s telescope of any significance might start around two or three hundred dollars, in the United States. There are less expensive ones, to be sure, and any telescope is better than no telescope. In fact, there is a huge market for used telescopes—find it if you’re on a budget! But here, I define “any significance” as a telescope flexible enough for looking at many categories of things and able to be accessorized.
I began by using one of those and putting my iPhone up to the eyepiece of my first telescope. This would be the very first astrophoto I’ve ever taken, and you can see it on the right. There’s a lot of light leaking in, and the photo is really indistinct. All of this could have been easily fixed with a twenty-dollar accessory, which would have held it still, at the right distance, and blocked out the extra light. This is a perfectly fine way to get started.
Later on, I took some better moon photos doing basically the same thing with another camera. The only improvement I made was just holding it a little differently and manually focusing (the manual focus is the reason I switched out the cameras). I never really subjected these photos to any real editing besides some light touching up in Apple Photos.
Nevertheless, these were pretty challenging to take because I was literally just holding up the camera to the eyepiece of the telescope, making sure they were lined up perfectly, and moving the telescope to track the moon at the same time. I wish I’d gotten that smartphone accessory, but I decided instead to upgrade everything.
What kind of camera do you use? Does it have to be a fancy camera?
I currently happen to use a Sony α6300 E-mount camera with an APS-C CMOS sensor. This is a mirrorless camera, meaning it’s significantly smaller and lighter than a full DSLR camera but gives me a lot more control than either a smartphone camera or most point-and-shoot cameras. I chose this one with astrophotography in mind because of its extremely rapid autofocus (when using a lens, good for wide-field) and its ability to take 4K video, but I use it for general photography too.
A lot of people taking pictures of the sky at large seem to use DSLRs because of the quality and size of the sensor and because of the fine control it gives them (allowing them to expose for a long time, for example). When it comes to the telescope astrophotography, I almost always see people using a purpose-made CCD (charge-coupled device) camera. These cameras are almost like purpose-built webcams that strap onto the back of the telescope and are specially made for gathering space photos. They can run a few hundred or on up.
All that said, the difference in sensor really becomes relevant once you start using techniques that exaggerate the noise it gathers. A smartphone camera is a fine place to start, and remains part of my repertoire because it’s just so damn easy. These phones’ cameras are becoming indistinguishable from mid-range consumer point-and-shoot cameras.
What kind of stuff can I see through a telescope with my eyes?
Oh, all sorts of things! But they may not look as you expect. Telescopes do funny things that defy all our expectations.
Everything you see is turned upside down. (There are a few telescopes which don’t do this, but they have drawbacks and are seldom used.) This isn’t a big deal for looking at the sky, usually, but makes it hard to orient yourself.
Everything is much brighter. Depending on the aperture (width) of your telescope, a sky which appears pitch black will have a soft blue glow. The moon will become bright enough to leave spots on your vision and even be painful to look at for long. Planets will glow like headlights in the distance.
Stars will be much brighter and much more numerous. There’s nowhere you can point your telescope that some stars won’t be visible, especially in a dark area. A star will never appear to be more than a very bright point at most, though, unless the star is actually something else (two stars, a small nebula, a planet, or whatever). No telescope on earth can zoom in enough to see a star as more than a point.
Star clusters will look like bright scatterings of jewels, like little private Milky Ways only you can see sometimes, or like indistinct smudges at other times. The Pleiades will have bits of dust around them.
Bright nebulae will look indistinct to the naked eye and will vary a lot by light pollution. The Orion Nebula will be dark and dusty and look as if there were glowing pearls seen on a sea floor among sand. The may be difficult to make out any color if you’re standing in a city or using a smaller telescope.
How much a telescope can magnify depends on the eyepiece you use, its focal length, and its aperture. You change out the amount of magnification by using different eyepieces. The more you magnify, the dimmer the image becomes, and the more distorted it gets. Beyond a certain point (which differs by a telescope’s length and aperture), there’s no point in trying to magnify further. Distortions come from both the air moving around constantly and the bending of light itself. (Imagine using a magnifying glass—it magnifies slightly more as you hold it away from the subject, but up to a point, and beyond that, it just distorts.)
Planets and the moon will appear to shimmer, as if viewed distantly on a very hot day. In particular, most of the time, focusing on a planet will seem challenging, as if just when it’s about to come into focus, it goes right back out. There are times when you’ll have better luck than other times—when the seeing is good.
Unless you’re using a telescope with automatic tracking, everything is going to move—fast. To be sure, this is the Earth’s motion, but you’ll be surprised just how quickly things move out of view. When I first began looking at planets, I had perhaps twenty seconds to look at them before they were totally out of view. The less magnified they are, though, the less the motion is magnified.
It’s one thing to know all these things. It’s another to put your eye to the eyepiece and look and make sense of what you’re seeing. It literally takes practice, over minutes, hours, and several occasions, to get better at actually seeing what you see because they are so outside of our experience.
You’ve never really seen anything like, say, the Orion Nebula—you’ve seen evenly exposed, two-dimensional halftone prints, or you’ve seen pixellated digital images constrained within the sRGB color gamut. The actual celestial body—the scintillating, shimmering indistinct dust cloud, stars littered within it, fanned out between the poles of dimness and brilliance, filled with colors and forms you’ve never seen before—is indescribable. Our brains are not designed for this sight, and our lives have not prepared us for the experience.
What objects are there? Is it only Earth’s moon and some planets, or are there other things you can look at?
I’ve named several already, but lemme categorize!
Yes, there’s the moon.
There are planets! The classical ones (out to Saturn), and some people like to look at the ones further out.
Then, there are the planets’ moons! I’ve seen photos and even animations of the Galilean moons transiting Jupiter.
When there are comets around, people with telescopes can spot these well before the rest of us.
Further out, there are
variable stars (ones which slowly get brighter and dimmer);
star clusters, like the Pleiades;
bright nebulae like the Orion Nebula or the Crab Nebula; and
galaxies like the Andromeda Galaxy, Triangulum, etc.
A guy looking for comets in the eighteenth century, Charles Messier, got really annoyed by all the smudges he saw which were not comets, and he began listing them as Messier objects. The current list is a decent smattering of deep sky objects, all of which are decently easy to observe with a telescope.
Can you see satellites?
I originally got this question in a longer form, with several questions clustered together that I wanted to answer at once.
can you see GPS satellites? (or are those in geosynchronous orbit so no? what even is geosyncronous orbit?) can you see the international space station?
In general, low-earth-orbit satellites are often visible. Their motion usually makes them obvious. They’ll be a brightish dot drifting along very obviously. It won’t generally be able to see much more detail than that. It’s possible to distinguish from an airplane because an airplane will often have blinking colors to it and will appear to approach from the horizon, grow faster and brighter, and then dim and appear to slow toward the opposite horizon. Satellites are usually singular, steady lights which move at a fixed speed.
One phenomenon to know about is the “satellite flare,” also known as an “Iridium flare,” where a satellite will suddenly grow bright in the sky for a moment and then dim again. This is where a satellite catches the light from the sun on its surfaces (such as its solar panels) and reflects it back down to us.
The International Space Station is the brightest satellite of all and is very often visible. It moves very quickly because it circles the entire earth in about ninety minutes, which makes photographing it challenging. That doesn’t mean people haven’t tried—and succeeded! I’m not an expert on this, so check out this rad article on spotting and photographing satellites, including the ISS, which includes some ISS photos!
GPS satellites are not in geosynchronous orbits. They’re in medium earth orbits, about twelve thousand miles above the earth, which is fifty times further away than the ISS or most other satellites. They take about twelve hours to go around the earth. I don’t really know precisely how big GPS satellites are, but if they’re about the size of a bus, they subtend maybe roughly a tenth of an arcsecond at that distance (based on some quick back-of-the-envelope math I did). This article says the limiting resolution of the atmosphere is usually about two or three arcseconds (rarely less, but never a tenth). This is assuming the satellite puts off enough light to be visible at such a small size and you know precisely where to find such a minuscule thing. It’s probably out of the question that you could see a GPS satellite, even under the best conditions and with the best telescope.
Geosynchronous orbits are twice as far up still as GPS satellites, perhaps twenty-five thousand miles up or so. This far up, a satellite moves along slowly enough that it’s always above the same longitude of the earth, and if it were visible (though it wouldn’t be unless it were huge), it’d appear not to move eastward or westward. If the satellite is above the equator, it’s called geostationary, and the position of the satellite would appear to be fixed like a star.
These orbits are useful for communications and weather satellites, but this is getting off the subject of astrophotography, so I won’t get into the mechanics of this.
How do you figure out when the stuff you want to see is going to be in the sky? Do you use an app or something?
I use an app called SkySafari. It has a feature that can prepare viewing lists for a given evening. I can also choose a time and see what the sky looks like at that time. It helps me determine what magnitude a given object will have, sort by magnitude or category, and other features.
The moon, viewed through a telescope, is indescribably vivid, immense, and gorgeous. Even looking at it through binoculars can give you a sense of what I mean. Where it’s always been a perfect sphere with indistinct features on it, it becomes a landscape with mountains casting shadows, basalt plains, and craters that look as fresh as when they were made.
If you mean man-made things, unfortunately, no. Man-made artifacts on the moon are much too tiny. The moon is huge.
Why do you love having a telescope?
The first thing I remember loving, when I was old enough to love something, was space. I began with early-1960s Childcraft books and encyclopedias my grandma had when I was very young. The information they had was dated, sketchy, and incomplete, making everything seem mysterious, dim, and distant. Most things were still shown as illustrations, or at best, blurry photos. For example, at that point they didn’t even contain any clear photos of Mars, making the idea of canals seem reasonable. (There were no such things as space telescopes, and lucky imaging was just beginning to become feasible.)
Later, I got newer books from the library, with clearer photos and more precise facts, and I filled in the gaps in my knowledge. But the more I learned, the more complicated everything became. The new information didn’t just bring more answers—they brought more questions, more mystery. And the mystery drove me on.
It’s like this. I grew up in an isolated and insular place. My upbringing didn’t give me the opportunity to travel. I’d never seen mountains, deserts, big cities, foreign countries. Books describing space and all the things in it gave my imagination worlds to seize upon, and I imagined adventures to inhabit them. The subjects they described, the planets and galaxies and nebulae, loomed large in my heart and in my mind’s eye. Actual stars—and not celebrities—were my stars.
This is why I said, in my First Stargazing post, that seeing Saturn for the first time was like seeing a celebrity for me. It was literally difficult to accept the reality once it finally presented itself. I had always wanted to see these things with my own eyes, through no one’s filter. I had assumed they were out of reach until I looked into it and realized I was simply wrong. With a bit of equipment and a lot of practice, I could get started and see for myself the things I’d been reading about all my life.
When I first saw another galaxy, I had seen across a timeless gulf that no person could ever cross. I’ve seen a storm on Jupiter older than centuries. I’ve watched the Earth wheel under my feet so fast I could barely keep up. I’ve gotten lost among stars without names. Seen without the intercessor of someone else’s words, or someone else’s photos, new parts of the sky opened to me which had previously been ineffable and therefore lost.
Since I got my first telescope, I quickly discovered its abilities and limits, and I knew I wanted more. In fact, I wanted to be able to show other people what I saw, even if they couldn’t be there themselves. That meant learning how to do astrophotography.
I learned from reading online—and by using it myself—that my first telescope wasn’t suitable for astrophotography for a number of reasons. It was too light (being a large, empty tube for the most part), shifted too easily, not mechanized in any fashion, the Dobsonian mount was too simple, and I lacked any adapters to allow me to connect my camera to it. Taking a photo through it meant getting an adapter which would overweight the end, and so I’d have to constantly hold the whole thing still and counterbalance the weight, manually find and track to objects, and somehow manually follow the motion of things in the sky—with an altazimuth mount not designed for tracking, which didn’t have measurements, markings, or indices. To be honest, I was having trouble even finding objects in the first place, needing sometimes several minutes to track in on naked-eye objects (which would then flit out of view in seconds).
So I had to get a new telescope. I wanted something slightly more compact so I could carry it out to sites more easily, so I chose a Schmidt-Cassegrain telescope, which combines lenses and mirrors into a relatively compact body. I wanted to increase my aperture even more, so I looked for eleven-inch options and settled on a set from Celestron which combines the telescope I want with a computerized mount that can automatically find and track objects.
Putting all this together and learning how to use it has been a trial, but I’m getting better. It’s been cloudy here for weeks, so I’ve been messing around with it indoors learning how to align it and get it ready. A few nights ago, it finally cleared up enough to try it out.
Outside my backdoor, between the house and a nearby fence, there’s a sliver of sky through which the ecliptic passes, meaning I can watch planets rise and pass overhead. Recently, Jupiter has been rising early at night, right around the time the moon rises.
I took the pieces outside to the back walkway—tripod, mount, eyepieces, tube—and set up, switched on the mount, and did a quick alignment. Jupiter was low on the horizon to the east, climbing, visible as an unmistakably bright point. Once the tube was lined up close enough to see through the finderscope sitting on top of the main tube, Jupiter was obvious, a brilliant point surrounded by four smaller points.
I started with my largest (and least magnifying) eyepiece, the forty-millimeter one (giving me seventy-times magnification). It’s the one visible in the photo of the telescope above. Jupiter was clearly in view but out of focus, so I saw it as a large, diffuse disc with a large hole in the middle, the way light looks through a telescope which happens to have a large obstruction. In this case, the obstruction is built into the telescope, the center corrector mirror in the middle of the tube. I began focusing, and Jupiter came into view, no longer a point but a disc which was obviously wider than tall, with four points of light scattered in a line along the bulge. The shapes shifted and scintillated slightly as the air moved around.
This was my first time using computerized tracking, and I was so happy that the planet stayed in view rather than drifting just off out of view in a matter of moments. I found that I had to make adjustments after fifteen minutes or so, but these were pretty minor, likely because I didn’t do a proper alignment. When this happened, I could make them as fine adjustments with the handheld controller pretty easily, so it was so much less exhausting than my last experience. This automatic help made it easier to work on getting the best view I could.
Focusing in on a tiny object like a planet is a little frustrating because it’s plain to see there’s more detail there, but when you try to focus on it, you find yourself hitting a point beyond which it only gets blurrier again. Some of this is attributable to the limits of my optics, but most of it is due to the turbulence of the atmosphere, called seeing. From the ground, unless the circumstances are exceptional, atmospheric seeing limits the detail available to telescopes, meaning that more magnification usually doesn’t help.
Still, I tried. I brought out my twenty-five millimeter eyepiece, a shorter eyepiece with higher magnification (around 112 times). To my surprise, that gave me more detail this time. This proved to me that the tube itself was of higher quality than my previous telescope—or maybe just better seeing than last time. With careful focusing, I make out the cloud bands with my eye, and I thought I could even glimpse the Great Red Spot if I squinted. What I saw was a lot like the video I posted at the top of this entry (only brighter with more obvious moons).
I’ve never tried photographing a planet before, so I decided it was time to try now. I had found an adapter kit for my camera (a Sony NEX-6), so I took out the eyepiece and used the prime focus attachment, which essentially uses the telescope tube itself as a massive zoom lens, but without attaching any additional eyepieces. This meant no magnification beyond the tube’s own field of view, meaning that all the light the mirror was gathering was pulled into a small disc which shone too brightly to see any detail. Below is a picture showing roughly what this looks like.
After recording some pictures and video in this setup, I tried using an adapter that lets me use an eyepiece, getting me a lot closer to what I was seeing. I used the twenty-five millimeter eyepiece and the adapter to attach to the telescope, and after some careful focusing, I got several shots like the following one.
To get this shot, I had to fool around with the camera a bit, speeding up its shutter speed to cut down on the light that was obscuring details. This one was exposed for only 250th of a second. The moons are no longer bright enough to show up except as pale specks seen on zooming in. I applied some minor processing to improve the clarity, but that’s all. Otherwise, this is just a single snapshot of exactly what I saw that night.
What’s next? My current Jupiter shots impressed me more than I’d hoped for, but because of seeing, it’ll take some tricks to get more detail and more impressive photos. I’m looking into image stacking software which will let me combine many individual pictures into a single, more detailed shot. I’ll need it if I want to photograph deep-sky objects like nebulae or galaxies. And I’ll need to improve at aligning my telescope so it can track more accurately. It might take until summer, but I’ll update here when I try again.