“You know, ‘galaxy’ means ‘milky,'” I said, still looking up.
“What? No way,” my friend, who was stargazing with me with her own camera, said.
“Totally. ‘Milky Way’ is directly from Latin, ‘via lactea.'”
“So it’s not from the candy bar?”
I was taking photos with a new friend at her farm south of Portland. I remain extremely grateful to her for allowing me to do so because they allowed me to my first photos of the core of the galaxy unaffected by light pollution.
The photo above was processed somewhat delicately to improve the white balance and the colors and brighten things up a bit, but that’s more or less how it came out of the camera. Taking photos of the sky at large is a very different activity than taking photos of individual objects through a telescope.
Chiefly, there is no telescope. None of this post will discuss using a telescope. I took all these photos with my same mirrorless camera, the Sony α6300, and a tripod. To adapt this camera to wide-field night sky images of the Milky Way, there are two big differences from ordinary photography: for one, using a long exposure and high ISO, and for two, using a suitable lens.
When I started last year, I was practicing blind, experimenting in wintry months, guessing at settings, and using a 32 mm lens with significant shortcomings for night-sky photography. To make improvements, I’m grateful for information I got from Lonely Speck, which I adapted to suit me.
First, most of the job of collecting a night-sky image is accomplished by exposing with a high ISO and a long exposure period. This means trucking out to a dark site—this activity is absolutely impossible anywhere near a city and impractical in a suburb. You also have to have a camera capable of manual control over its ISO and exposure length, among other things.
For my early wide-field attempts, I was afraid to raise the ISO higher than about 1600. I took some experimental shots with the ISO as high as I could go, but few were in the middle ground. I assumed these photos would be unusably noisy. Therefore, the photos I which turned out best were at ISO 800, but to bring out any detail, I had to push them dramatically, such that they looked artificial.
The most important thing I read was an article on Lonely Speck about finding the best ISO which explained that ISO doesn’t increase sensitivity so much as it provides amplification of the underlying signal. ISO can be thought of as a gain control for the sensor signal. Quoting,
It’s a (very) common misconception that increasing ISO increases the sensitivity of a camera sensor. ISO doesn’t change sensitivity. Increasing ISO simply increases the brightness of a photo by amplifying the sensor signal. In the electronics world, amplification is sometimes called “gain.” …[W]e can “gain” brightness if we increase our ISO. … Higher ISOs won’t increase the visible noise in a photo. …A higher ISO will decrease the total dynamic range of the image…And, in many cases (like astrophotography), a higher ISO will actually decrease the visible noise[.]
I was amazed to learn this. The article goes on to explain the conditions under which this occurs and how. This meant that I was free to amp up the ISO on my photos considerably.
The other consideration was exposure length. Mostly, the goal is to expose as long as possible before stars stop being points of light and start being streaks. How long this takes is entirely a function of the focal length of the camera—that is, the wider the field of view, the smaller the points of light are, so the less noticeable it becomes when stars seem to “move” across the field of view.
The lens I had used before was a bit longer than typically used for Milky Way photography. It’s only able to capture about the size of a constellation. That meant that stars would appear to move if I exposed longer than about fifteen seconds.
Add these together, and I was taking in a lot less light than my camera was capable of. On top of that, my lens was not designed for astrophotography, meaning that it introduced significant distortions, called aberrations, to each photo around the edges.
Choosing a lens
I had noticed from the first images I took that I had weird comet-looking distortions around the edges of my photos, but I didn’t know why. All the bright stars ended up looking this way.
I figured I might be able to avoid these distortions by stopping down the lens somewhat (and I would have been right, as I later learned), but that would have meant blocking even more light.
Luckily, there was another post on Lonely Speck that explained all about these distortions, called aberrations. I learned that these shapes were a combination of coma (which caused the light from the star to smear inward toward the center of the photo) and tangential astigmatism (which butterflied the distortion apart parallel to the radius running from the center to the star).
These were in-built distortions of the lens. It’s not necessarily that I had a bad lens—indeed, this was a Zeiss Touit f/1.8, an extremely good portrait lens. It just wasn’t designed for work where spots of light in the periphery were meant to be precise dots.
I found out there are classes of lenses built by Samyang (also known as Rokinon lenses, among others) designed to minimize these aberrations, also having extremely short focal lengths (meaning, really wide fields of view). For my birthday in June, I treated myself to a Rokinon Cine CV12M-E 12mm T2.2 Cine fixed lens. This is the lens I’ve used for all the photos of the Milky Way since then.
The First Batch: Learning What’s Possible
I’ve taken two batches of photos of the Milky Way since getting the lens and figuring out the right direction for settings.
For the first batch, I went to Stub Stewart State Park and waited till about eleven at night. It’s summer, so that’s when astronomical dusk occurs, and you can look up and see the Milky Way (which is visible from that site, though a bit washed out). Being summer, as well, the core of the galaxy is visible in the south, which I’ve wanted to photograph for a long time.
I followed the instructions from Lonely Speck rather closely, with respect to ISO and exposure, and I found I got wonderful results. In this case, I exposed for twenty-five seconds, and I used ISO 3200. The results exceeded my expectations.
As I processed them later, I found that I captured a lot of the light pollution from the city (which was in the distance in the southeast), and that presented difficulties in processing the photos without bringing out splotches of unnatural color.
I consider my attempts from that night now to be middling, and my ability to process them have evolved considerably as well.
The Second Batch: Finding What Worked
I was extremely lucky enough to have a very helpful and happy friend who let me come to her farm and do more night-time photography. Because her farm was south of Portland, the core of the galaxy was facing away from all the light pollution. The photos at the top of the post represent some taken from this attempt.
Here at the farm, I decided to lessen both the exposure length of time (down to twenty seconds) and the ISO (down to 2000). The earlier settings, I had found, seemed almost too aggressive for the conditions, though I may revisit them if I’m at a darker site. But twenty seconds and ISO 2000 turned out to be perfect. The photos looked gorgeous right off the camera, almost without editing at all. The results had delicate bands of dust and light in them that were considerable easier to work with as I processed them on my computer.
I took enough that night that I’ve been able to find lots of different ways to process each and experiment with what I like. For some, I’ve tried wild color combinations and gradients. I’ve tried delicate forms of processing or pushing others as far as they’ll go. I’ve learned to duplicate a photo many times over so I can manipulate it in many different directions and compare the results.
This post has been about changes I’ve introduced to the photography process, and in a future post, I’d like to talk about processing a bit more (basically editing the RAW photos to make them pop). I’d like to get better at that first, though.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
We’re drowning each other out with shitposts, and I’m starting to suspect Twitter encourages it.
I literally have no idea what’s going on in my friends’ lives anymore because there are so many posts to wade through. Twitter gave up on the firehose approach of showing us everything, and now it tries to curate for us, but its algorithms have narrowed my age down to somewhere between thirteen and fifty-four, and it thinks I’m interested in—not kidding—dads.
To get back my firehose, I use Tweetbot. I just took a quick estimate of my extensive mute list (which I personally curate), and it weighs in at over eight hundred mutes at this point. The vast proliferation of image posts, a workaround for the strict character limit Twitter imposes, has made these mutes almost worthless, so I’ve had to mute entire people. Occasionally Tweetbot freezes when I mute a person who’s particularly prolific.
What am I muting?
Laborious, overwrought, played out jokes. (But usually these are spread in images, so I have to mute people. Sometimes they are blessedly hashtags.)
Conferences I’m not attending due to health reasons. (But often the conference has no official hashtag, and—in the case of Google I/O this year—I muted something like five hashtags, three people, and Google itself.)
People who repeatedly retraumatize me by putting violence, threats, horrific news and images, extensive and voluminous exegeses of injustice and hate, and soul-rending reminders of hatred (much of which is aimed at me) each and every day.
There is little I can do but mute these people entirely. Though they often need dozens or hundreds of tweets to spread their message, and though Twitter is itself a centralized and proprietary platform, they do not use any long-form, self-owned medium to promulgate their message. Why?
This is an extremely delicate and controversial point, I know. The anger and sheer revulsion at our world right now come in involuntary, peristaltic waves sometimes. And it’s hard to know who’s reaching whom with what message. Twitter itself bears a lot of blame for giving no one the tools for finer filtering of content. Rarely does this stuff come in hashtagged formats that I can selectively mute. There’s no way to exclude a single tweet or a thread for exclusion.
One-off news stories or other events.
In 2016, each celebrity death garnered a mute. I share in the psychic pain each caused, but each person’s reaction flared it anew, and it’s not that each person had one reaction, but some repeatedly brought it up for days.
In 2017, each news story echoes for hours over dozens or hundreds of tweets, despite every mute on the subject matter I can put up. Much of it is speculations or jokes.
Movie releases, sports events, galas and parties, press events, and a million other things I am literally not healthy enough to properly participate in, enjoy, or motivate myself to find interest in.
Downright awful, hateful stuff that my friends ought to know better than to share but just don’t.
“Drumpf” jokes, fat jokes, or intelligence jokes about Trump. Of all the fertile material (his malice, his incompetence, his apathy) to dredge up, why choose to band with the people whom we should be resisting? Why pile on his typos, ridicule his body, mock his lack of social grace, point out his unsophisticated food choices, or ride his faux pas? When you make fun of him for something, I assume you have forgotten people like myself who are suffering under his administration. Never forget what he is and what he has done.
Transphobic shit and people who are on my shit list for it: Erika Moen, Margaret Cho, RuPaul’s Drag Race, Tyra Banks, etc.
Shit I just can’t handle (e.g., horrific prison conditions), or other specific situations and people: “triggers”. Nothing anyone can do about this. I mute it the best I can.
I recognize that this problem can be read as mine rather than Twitter’s. My thought is, fewer tweets altogether comes out to higher value for each tweet. So I try to restrain myself a bit, though I’m not always successful.
But here’s the whole damnable hitch: the more restraint I show, the more likely whatever fewer tweets I do emit get lost in the noise. Or, alternatively: the more I value a tweet, the fewer people who will probably see it. And it’s cyclical. Someone who only tweets when it really counts for them might get fewer followers in the first place and will be more likely to have their tweet drown in the ocean.
I recently wrote close to seven thousand words about my astrophotography hobby. Then I shared it in a tweet since a blog post is a rather dormant thing on its own. I’ve been sharing about astrophotography for a little while, so I usually share on Twitter. It did get a decent amount of engagement, but I discovered something strange happening afterwards. I noticed after a while there were still swaths of friends who had never seen any of my tweets about the subject at all.
Haven’t they seen any of my tweets over the last year about it? Any of the photos? Any of the posts I’d written on this site and then shared? No. None of that, they would say. They didn’t even know I had a website.
If this had happened just once or twice, I might’ve dismissed it. But this has happened repeatedly. These tweets just get lost somehow. If it’s not a marathon thread, or tweeted at the precise right moment, or retweeted by the right person, or some other magical thing I haven’t found, then it gets mislaid, I guess. I’m not sure what’s going on.
Or, maybe I do. Twitter turned off their firehose last year. Facebook did years ago. This game went pay-to-play. Either you’re already a person who drives a lot of engagement, who gets visibility, or you pay for the same.
Except, it would be super clumsy to literally have people pay to get their tweets seen. That’s just an ad, and it’s going to look like an ad, and nobody wants to click an ad, right?
But, like, right now, some people are living as ads. They drive particular kinds of traffic, specific kinds of engagement. They don’t look like ads. They target niches with surgical precision. They do this by churning out bulks of, more or less, “pulp” tweets. Each drives more engagement and synergistically works with the others.
It doesn’t particularly matter what they post. Could be they shitpost a very specific thing that a very specific set of weird Twitter just really likes. Maybe @dril is an ad. Maybe you’ve seen more of @dril retweets than mine.
And once there’s a massive, captive audience, there’s potential for…something. Analyzing those people’s interests or behaviors? Subtly linking a video that happens to have an ad? “Yvan Eht Nioj”? I don’t know.
If this whole profit motive part of my post seems vague, it’s because I’m speculating on the mechanism. I’ve veered off into a conspiracy theory. I have friends who assure me I’m wrong, that I’m attributing to malice what is really staggering incompetence. Nevertheless, it’s likely Twitter will soon learn to capitalize upon making some people more visible than others. This is a thing Facebook has already done.
And indeed, this fact is beside my actual point. More to that point, our intemperate shitposting has abetted this imbalance of visibility and enables the profit potential. It justifies the algorithmic curation, and the rest—pay-for-views, filter bubbles, propaganda, outright abuse—follows from there.
I see no easy way to turn it back. It is what it is.
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 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.
Not that anyone asked, but here’s what skeeves me out about Mark Zuckerberg’s recent attempts to tour the nation and pretend to be a normal person to everyone he meets.
He hasn’t announced a single thing of the sort, but no breathing human can doubt he’s considering running for president of the US. His ambitions are as naked as they are clumsy. This comes from a man who has zero experience in the political arena and, when he inevitably announces, will only reveal the extent of his entitlement to a candidacy to the absolute apex of political accomplishment.
This ham-fisted tour shows his lack of agility or circumspection. So does running a company which fostered an attitude that speed trumped care, craft, or empathy. So does making statements about the death of privacy as a “social norm” and then walking it back.
The bottom line for me is, the whole thing bespeaks a man who simply feels he gets to run if he wants. Trump opened up a kind of permission effect: qualifications are now off the table. Now only volume matters. 2020 will see a field of clowns campaign, each jockeying for attention. And Zuckerberg is entitled to his captive nation.
I had read part of Brian May’s thesis, A Survey of Radial Velocities in the Zodiacal Dust Cloud, a week or so ago, and one section of it had stuck in my mind. Here I quote it below (ellipses mine).
It is remarkable that so few earlier records are available, since…the mysterious Light of the Zodiac ought to have been very conspicuous in the dark skies of earlier civilisations, comparable in dimensions with the Milky Way, and at its brightest, more luminous. … Could it be that our view of the Zodiacal Light is highly variable? Cassini was convinced that it disappeared completely between 1665 and 1681, and this man was certainly no casual observer. I have no solution to the puzzle. In the light of Cassini’s reports, along with Jones’s observations detailed below, and the curious dearth of references pre-Cassini, I am convinced that, despite the lack of any recent confirmation, we must admit the possibility that the Zodiacal Light has not always been what it is today.
The passage in full is worth reading, but the salient detail is that the zodiacal light may be a relatively recent phenomenon.
Later in the same chapter, another note got my attention, here quoted.
One of the great ‘surprises’ in space observations, as noted by Sykes et al (2004), was that the detectors on board the space vehicle Ulysses, once past the orbit of Jupiter, began to register particle impacts from the opposite direction to that expected from interplanetary dust particles, and at high velocities, clearly indicating an interstellar component to the dust cloud, which predominates at these distances from the Sun, but has been now detected, by the Hiten detector, even at 1 AU (Grün et al 1993).
Here we see that the dust particles are interstellar, as well, meaning from outside the solar system.
My mind returned to these two details today, and it occurred to me that the latter detail easily accounts for the former if I posit the explanation that the zodiacal dust cloud originates from interstellar dust through which the solar system has moved during its galactic orbit, encountering it in much the same way the Earth encounters cometary dust during its orbit, giving rise to meteor showers.
In fact, the zodiacal dust cloud’s interplanetary dust particles (IDPs) are located asymmetrically with respect to both the ecliptic and to the circumstellar disc, and I speculate it is for this very reason. (That is to say, in reading Brian May’s summarizations of other surveys’ findings of the locations of the IDPs in our solar system, they tend to be located in particular areas, not in a smooth ring.)
When I turned to chapter four of his thesis, Brian May’s interpretations of his results already include hypotheses about IDPs flowing in from the interstellar medium, both as the solar system moves through it and as the IDPs flow inward. These were vindicated by more recent observations.
The novelty of my speculations, which I’m sharing here, lies in the recency and asymmetrical nature of the zodiacal dust cloud, and the implications it has on understanding the nature of the galaxy.
By this, I mean that although the interstellar dust throughout the galaxy cannot be observed directly, we can extrapolate from our knowledge of the zodiacal dust cloud—our knowledge of the velocities and positions of the IDPs within our solar system—to use our sun’s past as a kind of lantern to shine a light on the dark, dusty path through which we have passed over the past centuries or millennia. In other words, if the spatial distributions of unseen interstellar dust in our galaxy are uneven, we can gain insight into these distributions.
If this is possible, I foresee implications in dark matter physics because it would help refine our knowledge of the mass of the galaxy, which would in turn help narrow the parameters of dark matter.
I’ve also wondered if this has climate science implications. I’ve read about hypotheses involving climate cycles tied to phenomena from the interstellar medium, and clouds of dust may be one such phenomenon.