Beginning Astrophotography: Fourth of July Moonshot

Waxing moon as seen on the Fourth of July at about 10:50 p.m. (large file)

On the evening of the Fourth of July, I was cringing every few seconds as volleys of illegal fireworks shot into the air a few houses over on my block. I was outside, poking halfway out my backyard garage with the telescope, looking at the moon to pass the time until Saturn rose over the treetops.

Conditions didn’t allow me any good Saturn photos, but the moon turned out to make a rewarding enough target. I took a minute and a half of video and fifty-eight photos. It probably seems silly, but I’ve wanted to stack the photos from the moon for a long while. The moon is an easy enough thing to see in plenty of detail, but it’s difficult to show it as a vivid, three-dimensional object—the way it looks through a telescope—in a photo. So much gets lost in the translation from eye to sensor, and much of this experience gets swallowed into the seeing disc at the moment of capture, maddeningly blurred at the final moment.

Individual photo of the moon, cropped
Individual photo of the moon, cropped (large file)

For comparison, here’s an individual photo of the moon that’s been converted from RAW and cropped but otherwise not tampered with at all (ISO 400, f/6, shutter speed 1/800 s). You might have to click on it to see it larger to get a sense of the difference I mean. You’ll see the same details from the image above, but they’ll be indistinct. In particular, look at the edge of the basalt plain along the top limb, where the terminator crosses it. Or look at the craters along the lower part of the terminator. I look at that and think, oh, yep, that’s the moon—no news there.

Last night, I tried stacking the frames of the video to get more detail, but the results were only so-so. I was pretty dissatisfied, and because I expected to get more, I kept pushing the image, getting distortions in some of the higher contrast parts of the image. I used all kinds of filters to get what I wanted (deconvolution filters of all sorts, wavelet sharpening, unsharp masking, custom convolution filters, all sorts of contrasting and denoising), but I just made things worse.

I am not sure why stacking from a video gave me a poorer result. The same problem probably limits my planetary photos as well, so it’s worthwhile figuring out. It might be some aspect of the sensor, or it might be that I’m using too many photos in the final stack, more than needed. Maybe I didn’t align the frames properly.

In either case, I took all the RAW photos as a backup, so I turned back to those today and stacked them. All the photos were taken with the same settings: ISO 400, f/6, shutter speed 1/800.

I’ve discussed this process before, but to run it down again,

  • I converted all the RAW images to TIFF;
  • I used AutoStakkert!3 (a beta version of the program) to load them up as individual frames, then stacked all forty-seven of them; and
  • I loaded the resulting TIFF from that stack in AstraImage and, after much experimentation,
    • first applied as much wavelet sharpening as I could before distortions became apparent, and
    • then applied a very small amount of unsharp mask.
Screenshot of AutoStakkert!3 being used on the moon photos
Using AutoStakkert!3 to stack the Fourth of July moon

I’ve experimented a little with stacking, changing parameters here and there to see how the result changes, but mostly I’ve been trusting that it’s doing the job properly and concentrating on seeing how much I can get out of AstraImage, since that’s quicker. I’ll load up the stacked TIFF, make a change, and save a version. Each change, I’ll save, and when I’ve gone down a path too far, I’ll back up to a version that I want and start down a new path. With them all in the same directory, I can then open them all at once and shift between them quickly, as if I were using a blink comparator, to see which changes helped and which hurt.

After I was done with all these things, I took the photo over to Apple Photos to tweak the colors, levels, and contrast a bit and to share.

Beginning Astrophotography: An Update on Jupiter

Image of Jupiter made from video taken on the night of 18 June 2017, about  10:00 p.m., from which 40% of the individual video frames were stacked.
Image of Jupiter made from approximately two minutes of 4K video taken on the night of 18 June 2017, about 10:00 p.m. Video was taken with a Sony α6300 camera looking through a 25 mm Plössl eyepiece on an eleven-inch Schmidt-Cassegrain telescope. Image was made from which 40% of the individual video frames stacked.

Beginning Astrophotography: Saturn

Recording a video of Saturn through a 25 mm Plössl eyepiece.
Recording a video of Saturn through a 25 mm Plössl eyepiece.

I have waited a long time since I first saw Saturn two years ago through a telescope to see it again and properly photograph it. For a number of reasons, it took until last night before I finally got the chance.

By changing a few things, I improved my Saturn photos considerably over my previous Jupiter ones.

  • I realized I needed to collimate my telescope. This means that the secondary mirror had gotten very subtly out of alignment with the primary mirror, and I had to use a tiny screwdriver to move it back into alignment. Once I did this, I found I was able to focus on things better. This also meant that I could use higher magnification.
  • I took advantage of the more precise focus by putting a Plössl eyepiece into one of my camera adapters. This allowed me to magnify what it saw and gather more detail.
  • Finally, I’ve been searching out better software workflows and practicing with the software I have to get better at image stacking and polish the results. I’ve mostly replaced PIPP and RegiStax from my Jupiter post.

Example video clip

With these improvements, last night, I took a few longer videos at different focal lengths and with different camera settings. Below is a short ten-second clip as an example of what I captured. It was taken with my typical Sony α6300 connected to my telescope with an adapter through a 25 mm Plössl eyepiece. The video is at 4K resolution.

Software

The core activity of the software I’ve used for improving the images I’ve taken is stacking. What and how I stack ultimately determines which software I use.

I had already been frustrated by RegiStax due to its complexity, instability, and inflexibility. From searching online and reading others’ experiences, they often stacked in another program and used RegiStax for its wavelet features only. The most popular program for stacking appeared to be one called AutoStakkert!.

Once I replaced RegiStax, the rest of my workflow changed too. I began practicing with AutoStakkert and found that it minimized my need to use PIPP. I could essentially load a video directly into AutoStakkert without preprocessing it as much.

From there, the program itself was (relatively) more straightforward to use. There are detailed guides for its use available online, so I won’t recapitulate its usage here—I’m still learning it myself.

Screenshot of AutoStakkert! after use on a video of Saturn showing its features, parameters, and timings.
Screenshot of AutoStakkert! after use on a video of Saturn showing its features, parameters, and timings.

Once it’s finished with the source video, it has taken all the individual frames and combined them into a single image that looks, actually, not that useful, like a ghostly blurry image.

Stacked but unmodified image of Saturn
Stacked but unmodified image of Saturn, before applying wavelets, sharping, histogram stretching, rotation, etc.

AutoStakkert! doesn’t replace all of RegiStax’s features, such as the wavelet filters, so you’re left to do that on your own. I could load this into RegiStax to finish up then, but I found another piece of software called Astra Image that’s dramatically simpler and more powerful to use. This is the first piece of software I’ve mentioned so far that actually has cost money. It has a “Wavelet Sharpening” feature that brings the details right back out. In the very same program, I can apply additional sharpening, denoising, contrast, saturation, and  flipping over the vertical and horizontal axis.

After all that, I get the final image.

Final image of Saturn formed by stacking 40% of the frames of approximately two minutes of video.
Final image of Saturn formed by stacking 40% of the frames of approximately two minutes of video.

Beginning Astrophotography: Deep Sky

I’ve spent so long looking at Jupiter in my backyard that I finally decided I wanted to see if I could spot anything outside of our solar system. Light pollution sorely inhibited my efforts, but I managed to capture a few things! I’ll keep this post short and just share two representative photos I took.

Each photo has a small bit of blur in the direction of about eleven o’clock. This is due to a slight jostle that happened as I lifted my finger from the camera shutter. I’m still quite new at this—these are the first extended exposures I’ve taken through a telescope—and I didn’t know how much this would show up. Next time, I’ll use a remote shutter or a timer. Update: Now that I’ve had some time to experiment with photos taken later without any camera shake at all, I’ve realized this blur was likely due to collimation error.

Ring Nebula

The Ring Nebula
The Ring Nebula photographed on the night of 20 May 2017 at 23:10 PDT

One of the best things I saw last night was the Ring Nebula. It was one of only two nebulae that I was able to get any sort of decent view of, given the light pollution. It’s a planetary nebula, and it subtends a disc roughly the same size as a planet like Jupiter. It, like all the rest of the photos in this post, were taken by my usual setup, with my telescope stopped down to f/6 by a reducer (which makes everything seem smaller and brighter). No physical filters were applied (meaning, nothing to block out light pollution). It’s been edited lightly to remove the light pollution haze and bring out the color and contrast.

Seen with my actual eye, it looked largely like this photo, but the color was more difficult to make out. It looked ghostly and pale, like a puff of vapor. Color was a little easier to see if I looked just off to the side of it.

Hercules Globular Cluster

Hercules Globular Cluster photographed on the night of 20 May 2017 at 23:01 PDT
Hercules Globular Cluster photographed on the night of 20 May 2017 at 23:01 PDT

I didn’t expect a globular cluster to be any interesting to look at. Most of the targets of opportunity from my backyard were globular clusters, though, and I looked at a few. I looked at the Hercules Globular Cluster (Messier 13) first. It was like a diffuse scattering of dew drops spread on the petals of a flower too dark to see. Each of the individual stars were a bit difficult to see individually. But it photographed decently well.

I saw, and photographed, a couple of others, but their photos were not entirely as impressive, and I failed to note which was which, so I could not properly identify them for this post.

Filters

Future photos I plan to take will use either a narrowband O-III filter or a broadband UHC/LPR filter. The former permits a specific sort of light to pass through, while the latter tries to filter out particularly problematic types of light. Either should help both with photography and viewing. So hopefully the next few photos will be improved! I’ve learned a lot already.

Beginning Astrophotography: Journey to Jupiter

An enhanced photo of Jupiter, as viewed from the earth from an amateur telescope
Jupiter on the night of 3 May 2017, just before 9 p.m.

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.

I have also written a separate post answering questions I frequently get when I share photos like these. If you’ve become curious about this hobby for yourself, it may help you set expectations about what amateur astrophotography involves.

The Outlay

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.

First Telescope

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.

When it arrived, I took it out that very night and saw Saturn.

Second Telescope

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 SchmidtCassegrain telescope kit, including a computerized mount. A SchmidtCassegrain 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.

The adapters are usually pretty (relatively) inexpensive. One I’ve used recently is on Amazon, and an earlier adapter kit costs the same.

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.

Focus and Seeing

Once my telescope was assembled and ready to use for the first time, Jupiter provided the first target of opportunity from my house. The first challenge I had was focusing on Jupiter properly.

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.

Seeing Further

Individual frame from a video of Jupiter
Individual frame from a video of Jupiter

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.

Lucky imaging

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.

Preprocessing

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.

Screenshot of PIPP

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).

Stacking

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.

  1. Hit “Select” in the upper left and open up all the images to stack at once.
  2. 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.)
  3. 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.
  4. Then click “Align”. This takes a moment.
  5. 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.
  6. 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.
  7. 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.

Beginning Astrophotography: Frequently Asked Questions

Wide-field view of Andromeda Galaxy, individual photo taken without a telescope
Wide-field view of Andromeda Galaxy, individual photo taken without a telescope

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?

Yes!

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!

Screenshot of DarkSiteFinder.com Light Pollution Map near Portland, OR
A map of the light pollution around Portland, Oregon

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.

Photo of a detail of the moon taken by an iPhone through the eyepiece of a reflector telescope
My very first astrophoto taken of the moon through the eyepiece of my first telescope with an iPhone

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.

Photo of the moon taken through the eyepiece of a reflector
Another photo of the moon taken through the same telescope ten days later

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.

My post Beginning Astrophotography: Jupiter Ascending describes the first upgrade I made. In Beginning Astrophotography: Journey to Jupiter, I go into much greater detail about my equipment choices, budget, and capabilities—but remember that my choices don’t have to be your choices.

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
    • double stars;
    • 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.

I also use a website called the Clear Sky Chart to know whether conditions nearby will be amenable to observation. Here’s the Clear Sky Chart for Portland. And here’s the chart for a state park where I can more easily access dark sky conditions.

Can I see cool stuff on the moon?

Depends on what you mean by cool!

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 primordial storm on Jupiter older than anyone alive today. I’ve felt 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.