Opinion: We need to move our astronomical observation equipment off of Earth and onto other bodies, especially radio astronomy, which, unlike telescopes that operate in other wavelengths, is still affected by Earth's emissions in LEO/near-Earth space. We should put a radio telescope on the far side of the moon [0] to benefit from the thousands of kilometers of lunar material separating Earth's emissions from telescopes.
Unfortunately, that seems to be the only solution.
However, it has serious disadvantages. It will exclude the poorer from astronomical research, except within the limits enabled by whatever cooperation the richer will be willing to do with them.
For the richer, that will make astronomical research much more expensive. When even USA, who claims to be the richest country, cuts a lot of the scientific funding, this makes likely a great reduction in the research targets that could be accomplished, even if a Lunar array of telescopes and radiotelescopes and communication relays for them were approved.
While professionals might still be able to do some work, the amateurs will be able less and less to enjoy the sight of the distant Universe.
There are already many years since I have become unable to see the sky that I enjoyed looking at when young, because it cannot be seen from the city where I live, due to light pollution (and high buildings). To see it again, I would have to go somewhere up in the mountains, far from a city or village, but I have not succeeded to do this recently. Even there now you can hardly look at the sky without seeing satellites, and it will only become much worse.
Nowadays there are many children who have never seen even once the sky that our ancestors were seeing every night, so many passages from old texts that mention the sky are unintelligible for them.
> It will exclude the poorer from astronomical research, except within the limits enabled by whatever cooperation the richer will be willing to do with them.
Isn't it the case that most astronomical research uses source data from large telescopes and sky surveys? An example is the Rubin Science Platform [0] which makes available images and metadata from the Rubin Observatory along with compute and APIs?
I get what you're saying, but poor people want cheap internet/phone connectivity. They can't afford telescopes anyways.
And starlink (and the like) have more uses beyond good remote connectivity. They're a big reason why Ukraine didn't lose to Russia. They're also a potential avenue for people in oppressed nations to talk to the rest of the world (eg: Iran has a death penalty for starlink usage to counter this point).
> Our telescopes actually need the (or at least an) atmosphere to function.
What about Hubble, Chandra, Spitzer, JWST, etc? As of my understanding, the only reason we haven't built radio and and other long-wave telescopes in space is because of their impractical size preventing them from being deployed in orbit.
> There are some classes of observatories, which you cannot build in space but which are still affected by satellites to some degree.
This shows that wavelengths between ~10cm and ~10m are largely unaffected by the atmosphere, so you wouldn't gain much from putting receivers of those wavelengths in space. Spitzer and JWST (IR), and Chandra (x-ray) operate in bands that are generally blocked by the atmosphere, and Hubble gets better images than a similarly sized earth-based telescope because of the atmospheric distortion (stars don't "twinkle" when you're in space), however there are still earth-based visible light telescopes because you can more easily build a massive one on earth than in space
Imaging Atmospheric Cherenkov Telescopes, we detect optical light emitted by high energy particle Cascades in the atmosphere to observe cosmic gamma radiation.
The particles need the atmosphere to interact, Cherenkov light is only emitted in an optical medium and because it's optical light we measure we are affected by satellites. Not as strongly as optical telescopes though, because the air showers last for only tens of nanoseconds.
What? The atmosphere gets in the way. Ever heard of an (amateur/)astronomer talking about 'good seeing'? That's when the atmosphere is hindering you less than usual.
The limiting factor of passive optical telescopes on earth is the atmosphere.
IMO, everyone that launches/operates a constellation should pay for launch of large telescope every 5-10 years (assuming science organizations can fund/build them).
Sure, there have already been some launched and predictably they are only adequate to look at the bright stuff we already knew about from the big telescopes.
A small telescope is just a small telescope even when you put it in space.
> . We should put a radio telescope on the far side of the moon [0] to benefit from the thousands of kilometers of lunar material separating Earth's emissions from telescopes.
Do you really think a starlink style installation won't be put in orbit of the moon before such a telescope could be funded?
Those rules won't last long once (IF) there are significant numbers of people on the moon. The rules are easy to agree to today (50 years ago) because nobody could do anything otherwise anyway. Once the rules are getting in the way of a significant number of people they will change.
I make no predictions how they will change, but the current rules are obviously unworkable if significant numbers of people live in space. I also make no predictions on if we will ever get significant numbers of people living in space - there are a lot of hard/expensive problems that may not be solvable.
Starlinks are already spewing out into supposedly protected radio bands on Earth, good look getting these rules respected on the Moon when they aren't here.
Computational photography has long been table stakes for astronomers. They just need to up their game on satellite rejection algorithms. Satellites look nothing like stars, and as such are pretty easy to remove with software. Pictures like this which leave them in are just there to make a point.
True. But that’s never the framing you hear from astronomers. It’s how the satellites are “ruining” the pictures, like this whole thread.
The SNR degradation isn’t even very much. Noise goes down by 1/sqrt(N) samples. In a stack like this might have 5-40 images depending on how they did it. Typically a satellite will only show up on one of those images for a given pixel. So by excluding that image from the stack that pixel’s noise would go up by a ratio of sqrt(N/(N-1)) which for 5-40 images is between 12% more noise and 1% more noise. Only the pixels with satellite tracks.
True there’s more noise if you remove the satellites. But it’s probably only a few percent noisier, and only in the places where the satellite flew. Add a few more images to the stack and accept that the world is changing.
So what? Astronomy doesn’t actually produce anything meaningful.
Hell, astronomers were telling us the sun orbited the earth for 99% of human history. Shoot forward to the present day and they can tell us… the universe started at some point somehow. Great job guys. Really earning those billions in grants.
My time to shine! I've spent yesterday morning to track the photo down and answer this question.
The APOD description is lacking.
Yes, this was an exaggerated stack of 153 four-second exposures (the rejection map of the satellite trails was added on top of the image), and the gaps happened when the camera took its time to save between two exposures.
Probably exactly that. If you take a single 10 minute exposure (or really, anything more than a few seconds) you'll get noticeable star trails if you don't put your camera on a rotating mount. Stacking multiple exposures also has other nice benefits such as noise canceling itself out and being able to remove satellite trails.
Last time I did astrophotography was a few years ago, before Starlink made the problem considerably worse, but satellite trails were relatively easy to remove with stacking. I'm sure it's harder now but definitely still possible, so I'm assuming in this case leaving them in was done on purpose to highlight the problem.
EDIT: Looking better at the picture, I belive this was taken with a star tracker and then composited with a shorter exposure of the foreground. Notice how the foreground, even far away, looks considerably blurrier than the stars, and how the tower in the background has some light streaks. This is exactly what you'll see if you use a star tracker. Rather than star trails, you'll have "foreground trails". This would explain why there are relatively few gaps in the satellite trails, since the exposures can be much longer.
Update: I was wrong, check max-m's sibling comment! The satellites just move really fast across the camera because they're in LEO, so they can traverse rather large distances before there's a new exposure and a small gap.
I am guessing, but I think it likely has to do with the shape and orientation of the satellite with respect to the sun and the camera. Depending on the relative positions, the brightness reflected off the satellite and reaching the camera will change over time.
I've taken long exposures using film (analog, so no stacking or any other funny business) and saw the same thing. I always thought they were planes but now it seems they may have been satellites. I'm curious if someone knows why this happens
Pretty much every DSLR/DSLM camera out there has a "bulb" mode that keeps the shutter open as long as you hold down the shutter button. I think my personal record is a 20-minute exposure.
As for actually holding down the button, you can either use an external wired shutter button that has a mechanical lock to hold it down, or you use a wired controller that has an electronic timer, or you use a software feature in the camera to set the bulb timer.
For anybody wondering, the reason not to do a single ultra-long exposures is noise.
There's an equilibrium between exposure duration, aperture, and ISO that gives the best results for the conditions with a minimum amount of sensor noise, and getting close to the equilibrium and stacking the images typically gives better results than one massive exposure.
I believe your claim about noise and long exposures is false. To start, I posit that there are three sources of noise:
0) Photon shot noise from the object that you want to photograph. This is an inherent and unchangeable quantum-mechanical fact.
1) Sensor read noise per photo taken. This increases with the number of subexposures.
2) Dark current noise per time and per temperature.
#0 and #2 only depend on the total exposure time, not the number of subexposures. #1 actually gets worse with more subexposures, but what you gain are the ability to reject satellite trails, bad mount tracking, cosmic rays, wind gusts, rolling clouds, and other transient artifacts. Whereas if you took a single hour-long exposure, it's essentially guaranteed to be ruined by something.
As for ISO, it is very commonly misunderstood. ISO amplifies photon noise and dark current noise, and changing the ISO doesn't make your images better or worse in these aspects. ISO in the form of analog gain can help boost the signal above the analog-to-digital converter noise, and that's what it's useful for. The MinutePhysics video explains excellently: https://www.youtube.com/watch?v=ZWSvHBG7X0w . More and more sensors these days approach "ISO invariance", where analog amplifier gain has about the same effect as digital gain (i.e. multiplying the measured numbers on a computer).
Exactly what I'm refuting:
> exposure duration
In astronomy, more is better. Get as much total exposure time as you can afford (e.g. time being at a suitable location, time spent monitoring the equipment, time under clear skies).
> aperture
In astronomy, more is better. Buy the biggest aperture you can afford - obviously, subject to constraints such as cost, weight, mountability, focal length. Also, telescopes don't have adjustable aperture blades, unlike general photographic lenses. You could put a disc cut-out in front of the telescope to close down the aperture, but that's just a waste of light.
> minimum amount of sensor noise
You get the least amount of sensor noise by reducing the exposure time and reducing the temperature (dedicated astro cameras have Peltier cooling). Note that although noise increases with time, signal increases with time faster, so the signal-to-noise ratio is proportional to the square root of time. So 100× more exposure time gives you a 10× better SNR.
> stacking the images typically gives better results than one massive exposure
This is the main falsehood that I wanted to address. Taking multiple images actually gives more noise overall, even if it's a tiny bit. But multiple images gives you much more processing flexibility and the ability to selectively reject things.
My Canon can do this without modification and its 8 years old. Switch to bulp and have an external mini device which you connect with a microphone cable and it creates the signal for shutter off after x minutes.
For extra long exposre its recommended to use also a stable powersource.
How is a 10 minute continuous exposure functionally different from 10 minutes of video with every frame stacked? In the former, each photodiode acts as a compositor for each pixel instead of whatever algorithm is chosen to combine frames in the latter?
You pay the read noise every time you read out the sensor and digitize the values. Also, you lose a tiny bit of time between exposures as the sensor resets itself. And you might have a bottleneck in moving the data off the sensor and saving the image. Furthermore, if you perform lossy compression on the video, then your digitally stacked image will differ significantly from analog stacking on the silicon sensor.
I fear this is only the start of it. A minimum of 3-4 constellations more will probably be launched in the near future (Russia, China, EU).
Their obvious dual-use nature makes them tempting, and a military target if a large conflict will take place in the near future. I hope their lower orbit will help any space junk burn up fast.
Add a black umbrella to each satellite: when they pass through the critical region where they are visible in the night sky while still being sunlit, pop the brollies up. We will fly them in the shade!
You could paint them black but they’d probably get quite hot.
Won't the shade then reflect the light instead? It's nighttime, so sunlight will be aimed up, from the Earth-based observer's point of view, so the shade will need to be pointed down in order to shade the satellite.
If you blow up a satellite, half of it will end up going slower and half will go faster. The slower bits will probably burn up nicely, but the faster bits will just elevate their orbit.
I doubt they will elevate their orbit by enough to be a problem. Some bits will come down in hours, some will come down in a year - even in the worst case where it takes out everything in low earth orbit in 5 years everything will be clear and we can start over. Higher orbits are the real worry, even the things slowed down mostly stay in orbit for centuries - but higher orbits are mostly a lot higher.
"LEO" is a big place, those satellites collided ~1.5x higher than e.g. the maximum Starlink altitude and the debris lifetime relationship is not a linear one.
FWIW, if you actually want to photograph a comet or anything that doesn’t move in the sky, you’d take multiple exposures that would make the moving light sources like satellites disappear. Taking HDR photographs like this has an number other benefits as well.
I, a taxpayer, would rather have a cellphone signal in a remote location than lots of amazing pictures of a comet. And I just don't see a solution or compromise that could work. The utility of neat picture vs full cell signal in a Montana canyon cannot be won by taking more pictures and showing me the problem. I made my decision already.
We don't need to give up streetlights to make huge progress. 20 to 50 percent of outdoor lighting is wasted. Just shielding streetlights would go a long way.
Well, isn't that good for you? The other seven and a half billion of us just get to deal with having our skies skidmarked like this with no choice on the matter.
It's strange to call it "skid marked" when the "skid marks" only appear when you apply complicated technology setups, and those setups can easily remove the "skid marks" also.
"Now, the orbiting satellites themselves only appear as streaks because of the long camera exposure, over 10 minutes in this case. On the contrary, to the eye, satellites appear as points that drift slowly across the night sky and shine by reflecting sunlight -- primarily just after sunset and before sunrise. "
Why doesn't the comet "streak" also, given the Earth's rotation? 10 minutes is a long enough window to have an appreciable impact on the comet's image. Or is it the case that the telescope is stabilized to the Earth's rotation?
Low earth orbit satellites orbit about once per 90 minutes, so in 10 minutes they go about 40 degrees across the sky. The comet is not even orbiting the earth, it's essentially fixed in the sky. The earth only rotates about 2.5 degrees in 10 minutes. So the satellites streak is 16 times longer than the comets.
Let's start with "fixed in the sky" and qualify your frame of reference as the field of distant stars, or the celestial sphere. The common coordinate system is right ascension (RA) and declination (dec).
The GP question was about the Earth's rotation, which would be in terms of azimuth and altitude, and that question's been asked and answered. The key terms there: "equatorial mount" and "clock drive".
The comet C/2025 R3 (PanSTARRS) is in fact near its highest velocity (with reference to the Sun especially), being near perihelion while this photograph was taken. The comet is swinging around the Sun, and it was about 0.49 AU from Earth at the time of the photograph.
I chose an approximate time on April 27: in 10 minutes of wall-clock time, with the J2000 epoch, the comet's apparent motion is from RA 02h 49m 07.1s, dec +06° 02' 56.5" to RA 02h 49m 15.4s, dec +06° 02' 13.3"
That is a distance of 2' 11.13" across the celestial sphere. For reference, Venus is 11.6" wide in the sky as we see it this week.
24 hours later, we find it at RA 3h 08m 44.1s, dec +04° 19' 27.8". Its apparent motion was 5° 10' 46.02", which is approximately the width of your three middle fingers held together, at arm's length.
So, "fixed in the sky" is not a scientifically useful description of astronomical objects: we need to put that in terms of at least one frame of reference, and "apparent motion" which is how an observer perceives it.
Given that the moon is about 0.5 degrees in diameter from Earth, shouldn't we expect to see the stars and comet much more blurred than they are here though? Or the ground if it's stabilized against the rotation?
https://www.facebook.com/groups/Nachtfotografie/posts/264063...
Here is the original photo description in German.
See also my other comment in this thread.
But the tl;dr is that this was a stack of 153 four-second exposures with some gaps in the timelime when the camera took its time to save between exposures.
Hot take: We're in the first stages of building our own Dyson sphere and therefore comets are only useful in the context of capturing them for that purpose.
The idea of a Dyson sphere is that it's built around a star, in attempting to capture and utilize 100% of its energy output. So a shady shell around the Earth is not "the first stages" of a Dyson sphere, because our energy source is on the other side of the shell, and the orbits are completely different.
We do not need Starlink! It only provides service to 9 Million! People
We are a planet with 8 Billion People.
Do i want cheap and reliable internet everywhere and perhaps work remote? Yes. Should someone like Musk destroy our look into space for just me and my use case? No.
I do wonder if in 100 or 200 years if we do become interplanetary as a species, and technology advances if many of these satellites will just disappear from the night sky and it would be long since forgotten or if remembered only as a steppingstone towards an interplanetary future.
In the meantime, Starlink is the only thing that gives my sister in Puerto Rico access to the internet when the grid gets completely nerfed by a hurriance so she can tell us she's alright, well, that and landlines if she gets a power generator, otherwise, we're left to wonder how my sister and nephews are doing.
1. to keep this argument properly, you still need to see what the overall benefit for the whole society is and not just your little bubble. And putting a lot of satelites in sky, affects 8 billion people.
2. As i said, robust infrastructure would fix that too. Fiber under earth, backup energy etc.
Not to play the musk’s advocate, but there is a case to be made that proving internet access in remote places is more valuable than a perfect night sky. If you live in the cities you can barely see the stars anyway, so you’re not missing much. But in an austere environment, connectivity can be the difference between life and death. It also lowers the bar, encouraging more people to visit wild places and make them more likely to support their protection in more meaningful ways.
Speaking as someone comfortable with the outback night sky I'm fine without it thanks. So are pretty much all the locals and traditional owners of the Murchison Quiet Zone which is focused more toward radio silence overhead for SKA and such things .. so that all dovetails together.
If you're relying on starlink via a smartphone, you're basically unprepared in any case.
It is obvious that the 9 million current customers are just the beginning of where SpaceX wants to take Starlink access. Easy to imagine Starlink serving 1 billion + customers in the near future.
Its already quite cheap so why are people are not running to Starlink?
Probably because a land line has still less latency, doesn't consume that much energy and everyone has either a land line or mobile connection.
When Amazon Leo, Eutelsat, Telesat, Chiense and co enter the market, the margin will go down significanlty. The effort for handling the space and crashes etc. will increase.
Additional to this, my landline is stable. Its stable in heavy rain, with and without snow.
And the worst thing about Starlink and its adoption is the Satelite handoff every 15 seconds. I tried Starlink at my father-in-laws home and i was unable to use MS Teams reliable enough.
To finish Starlink off: it doesn't even properly scale. Right now they need v3 which they are not sending up because of the bandwidth limitation of one satelite. Then they have to route traffic through their satelites to were they have base stations. Now they also need to build basestations everywere together with sending up new satelites every 5 years.
1 billion customers? in that market? in the near future? never. The base stations we have are there, well connected, relativly cheap, very fast, very direct.
I've had no issue with starlink when using it at a friend's house, and I would be happy to use it myself if my internet provider decided to charge me more than what Starlink costs. And fiber has its own costs to install and maintain. A lot depends on the economies of scale for both systems, but to think that base station capacity and kessler syndrome fears are insurmountable obstacles is ridiculous.
To me, this is no different than the adoption of mobile phones: "Cell phone usage will never overtake landlines, we'll never fix the problems of bandwidth and cell phone towers that need to be installed everywhere. Sure there might be a market for a few million in the US but no more than that".
As others have mentioned in the thread, the narrow impediments to some night sky photography affect a much smaller portion of the population compared to the benefits these satellites already provide. Returning to the cell phone example, would be like opposing cell phone towers for impeding wildlife photography.
Are you or people around you do that for hours every night? Is this a deliberate activity, or are you including random quick glances? How often is yours or people's around you sky watching experience actually negatively affected by satellites?
Sun rises and downs is not affected by satellites, due to overwhelming brightness difference. For casual stargazers, light pollution is much more of an obstacle than the satellites. Plus, for half a day on average, the stars not available at all, unlike Starlink or other satellite services
I'm not a Starlink user either, I do like to look at the sky with naked eyes and telescopes, but I do not share the sentiment that it's imperative to keep it "pure" for the sake of whatever. Also, a personal anecdote, satellite spotting is quite fun :)
Done its beautiful https://imgur.com/a/tH39FAS
(telescopes in space looking outside should have happened long ago, lets just get it done man)
Yeah, I kinda get why astronomers are not particularly happy with satellite constellations.
And this is just the visible spectrum.
The situation is one order of magnitude worst in radio-astronomy.
It is fair to state that satellite constellations will certainly be the main obstacle to multiple major scientific discoveries in the next decade.
Opinion: We need to move our astronomical observation equipment off of Earth and onto other bodies, especially radio astronomy, which, unlike telescopes that operate in other wavelengths, is still affected by Earth's emissions in LEO/near-Earth space. We should put a radio telescope on the far side of the moon [0] to benefit from the thousands of kilometers of lunar material separating Earth's emissions from telescopes.
[0] https://doi.org/10.1109/AERO50100.2021.9438165
[1] https://en.wikipedia.org/wiki/Lunar_Crater_Radio_Telescope
Unfortunately, that seems to be the only solution.
However, it has serious disadvantages. It will exclude the poorer from astronomical research, except within the limits enabled by whatever cooperation the richer will be willing to do with them.
For the richer, that will make astronomical research much more expensive. When even USA, who claims to be the richest country, cuts a lot of the scientific funding, this makes likely a great reduction in the research targets that could be accomplished, even if a Lunar array of telescopes and radiotelescopes and communication relays for them were approved.
While professionals might still be able to do some work, the amateurs will be able less and less to enjoy the sight of the distant Universe.
There are already many years since I have become unable to see the sky that I enjoyed looking at when young, because it cannot be seen from the city where I live, due to light pollution (and high buildings). To see it again, I would have to go somewhere up in the mountains, far from a city or village, but I have not succeeded to do this recently. Even there now you can hardly look at the sky without seeing satellites, and it will only become much worse.
Nowadays there are many children who have never seen even once the sky that our ancestors were seeing every night, so many passages from old texts that mention the sky are unintelligible for them.
> It will exclude the poorer from astronomical research, except within the limits enabled by whatever cooperation the richer will be willing to do with them.
Isn't it the case that most astronomical research uses source data from large telescopes and sky surveys? An example is the Rubin Science Platform [0] which makes available images and metadata from the Rubin Observatory along with compute and APIs?
https://data.lsst.cloud/
I get what you're saying, but poor people want cheap internet/phone connectivity. They can't afford telescopes anyways.
And starlink (and the like) have more uses beyond good remote connectivity. They're a big reason why Ukraine didn't lose to Russia. They're also a potential avenue for people in oppressed nations to talk to the rest of the world (eg: Iran has a death penalty for starlink usage to counter this point).
> I get what you're saying, but poor people want cheap internet/phone connectivity.
Nope. Starlink is not a tool for poor people. It's first and foremost a tool for middle class living in rural area with poor connectivity.
As a comparison, it is estimated to that there is around 198M people in Nigeria with a Mobile phone connectivity. Compared around 67K Starlink users.
Mobile being around 2-3x cheaper than Starlink there (even without considering the hardware), it remains an upper middle class privilege.
[dead]
Our telescopes actually need the (or at least an) atmosphere to function.
There are some classes of observatories, which you cannot build in space but which are still affected by satellites to some degree.
> Our telescopes actually need the (or at least an) atmosphere to function.
What about Hubble, Chandra, Spitzer, JWST, etc? As of my understanding, the only reason we haven't built radio and and other long-wave telescopes in space is because of their impractical size preventing them from being deployed in orbit.
> There are some classes of observatories, which you cannot build in space but which are still affected by satellites to some degree.
Examples?
I believe we haven't built radio telescopes in space because we don't need to, and building them in space would be a lot more expensive.
https://commons.wikimedia.org/wiki/File:Atmospheric_electrom...
This shows that wavelengths between ~10cm and ~10m are largely unaffected by the atmosphere, so you wouldn't gain much from putting receivers of those wavelengths in space. Spitzer and JWST (IR), and Chandra (x-ray) operate in bands that are generally blocked by the atmosphere, and Hubble gets better images than a similarly sized earth-based telescope because of the atmospheric distortion (stars don't "twinkle" when you're in space), however there are still earth-based visible light telescopes because you can more easily build a massive one on earth than in space
Imaging Atmospheric Cherenkov Telescopes, we detect optical light emitted by high energy particle Cascades in the atmosphere to observe cosmic gamma radiation.
The particles need the atmosphere to interact, Cherenkov light is only emitted in an optical medium and because it's optical light we measure we are affected by satellites. Not as strongly as optical telescopes though, because the air showers last for only tens of nanoseconds.
What? The atmosphere gets in the way. Ever heard of an (amateur/)astronomer talking about 'good seeing'? That's when the atmosphere is hindering you less than usual.
The limiting factor of passive optical telescopes on earth is the atmosphere.
They are talking about very high energy gamma-ray telescopes, the Imaging Cherenkov Telescopes.
Agreed. It’s the only solution short of a ban on constellations.
IMO, everyone that launches/operates a constellation should pay for launch of large telescope every 5-10 years (assuming science organizations can fund/build them).
Its still worth while for every normal human to have access to space if the benefit of this stuff is not relevant for most people.
And with 9 million customers its not.
Any chance of CubeSat style of telescopes at some point?
Sure, there have already been some launched and predictably they are only adequate to look at the bright stuff we already knew about from the big telescopes.
A small telescope is just a small telescope even when you put it in space.
Or even out past the heliosphere/heliopause
> . We should put a radio telescope on the far side of the moon [0] to benefit from the thousands of kilometers of lunar material separating Earth's emissions from telescopes.
Do you really think a starlink style installation won't be put in orbit of the moon before such a telescope could be funded?
> Do you really think a starlink style installation won't be put in orbit of the moon before such a telescope could be funded?
There are ITUs rules that forbid that and the far side of the moon is declared as radio quiet.
Those rules won't last long once (IF) there are significant numbers of people on the moon. The rules are easy to agree to today (50 years ago) because nobody could do anything otherwise anyway. Once the rules are getting in the way of a significant number of people they will change.
I make no predictions how they will change, but the current rules are obviously unworkable if significant numbers of people live in space. I also make no predictions on if we will ever get significant numbers of people living in space - there are a lot of hard/expensive problems that may not be solvable.
> Those rules won't last long once (IF) there are significant numbers of people on the moon.
Maybe. If you believe we are heading to a situation with large numbers of colonies on the moon.
For now we are no way there and already struggle to just get back there.
Starlinks are already spewing out into supposedly protected radio bands on Earth, good look getting these rules respected on the Moon when they aren't here.
Computational photography has long been table stakes for astronomers. They just need to up their game on satellite rejection algorithms. Satellites look nothing like stars, and as such are pretty easy to remove with software. Pictures like this which leave them in are just there to make a point.
Not to disagree, but stacking a series of exposures with a sigma-clipped mean (or similar) should still get a nice image.
Exactly. It’s not that hard to remove the satellites. It’s almost easier than whining about it. But whining is more fun.
It is not hard to remove the satellites, but that is not free.
It reduces the signal-to-noise ratio of the image, making more difficult the detection of faint objects.
True. But that’s never the framing you hear from astronomers. It’s how the satellites are “ruining” the pictures, like this whole thread.
The SNR degradation isn’t even very much. Noise goes down by 1/sqrt(N) samples. In a stack like this might have 5-40 images depending on how they did it. Typically a satellite will only show up on one of those images for a given pixel. So by excluding that image from the stack that pixel’s noise would go up by a ratio of sqrt(N/(N-1)) which for 5-40 images is between 12% more noise and 1% more noise. Only the pixels with satellite tracks.
True there’s more noise if you remove the satellites. But it’s probably only a few percent noisier, and only in the places where the satellite flew. Add a few more images to the stack and accept that the world is changing.
It _increases_ the signal to noise ratio. It's a denoising technique, and that's what they do.
Compared to the processing already done to get data from astronomical data, yeah, it's essentially free.
So what? Astronomy doesn’t actually produce anything meaningful.
Hell, astronomers were telling us the sun orbited the earth for 99% of human history. Shoot forward to the present day and they can tell us… the universe started at some point somehow. Great job guys. Really earning those billions in grants.
Actually going to space has far more value.
Have you heard of Kessler Syndrome?
More satellites means higher risk on that happening and not going to space until all the debris of a collision deorbits.
Doesn't matter. We, as a society, have said we're willing to give up nature in exchange for money machines the go brrrrr.
Why are satellite trails not continuous lines
Is the camera exposure taking a few seconds of break between takes that get stacked later with some "missing" moments in between?
My time to shine! I've spent yesterday morning to track the photo down and answer this question. The APOD description is lacking. Yes, this was an exaggerated stack of 153 four-second exposures (the rejection map of the satellite trails was added on top of the image), and the gaps happened when the camera took its time to save between two exposures.
Here is a link to the original photo and it's description (German) by Uli Fehr: https://www.facebook.com/groups/Nachtfotografie/posts/264063...
Probably exactly that. If you take a single 10 minute exposure (or really, anything more than a few seconds) you'll get noticeable star trails if you don't put your camera on a rotating mount. Stacking multiple exposures also has other nice benefits such as noise canceling itself out and being able to remove satellite trails.
Last time I did astrophotography was a few years ago, before Starlink made the problem considerably worse, but satellite trails were relatively easy to remove with stacking. I'm sure it's harder now but definitely still possible, so I'm assuming in this case leaving them in was done on purpose to highlight the problem.
EDIT: Looking better at the picture, I belive this was taken with a star tracker and then composited with a shorter exposure of the foreground. Notice how the foreground, even far away, looks considerably blurrier than the stars, and how the tower in the background has some light streaks. This is exactly what you'll see if you use a star tracker. Rather than star trails, you'll have "foreground trails". This would explain why there are relatively few gaps in the satellite trails, since the exposures can be much longer.
Update: I was wrong, check max-m's sibling comment! The satellites just move really fast across the camera because they're in LEO, so they can traverse rather large distances before there's a new exposure and a small gap.
My guess is the camera itself was taking photos of shorter exposure and the final image was composed in post-production, yes.
I am guessing, but I think it likely has to do with the shape and orientation of the satellite with respect to the sun and the camera. Depending on the relative positions, the brightness reflected off the satellite and reaching the camera will change over time.
I've taken long exposures using film (analog, so no stacking or any other funny business) and saw the same thing. I always thought they were planes but now it seems they may have been satellites. I'm curious if someone knows why this happens
I'm not aware of a digital camera that can take a 10 minute continuous exposure, but maybe there are special astronomy cameras that can?
Pretty much every DSLR/DSLM camera out there has a "bulb" mode that keeps the shutter open as long as you hold down the shutter button. I think my personal record is a 20-minute exposure.
As for actually holding down the button, you can either use an external wired shutter button that has a mechanical lock to hold it down, or you use a wired controller that has an electronic timer, or you use a software feature in the camera to set the bulb timer.
For anybody wondering, the reason not to do a single ultra-long exposures is noise.
There's an equilibrium between exposure duration, aperture, and ISO that gives the best results for the conditions with a minimum amount of sensor noise, and getting close to the equilibrium and stacking the images typically gives better results than one massive exposure.
I believe your claim about noise and long exposures is false. To start, I posit that there are three sources of noise:
0) Photon shot noise from the object that you want to photograph. This is an inherent and unchangeable quantum-mechanical fact.
1) Sensor read noise per photo taken. This increases with the number of subexposures.
2) Dark current noise per time and per temperature.
#0 and #2 only depend on the total exposure time, not the number of subexposures. #1 actually gets worse with more subexposures, but what you gain are the ability to reject satellite trails, bad mount tracking, cosmic rays, wind gusts, rolling clouds, and other transient artifacts. Whereas if you took a single hour-long exposure, it's essentially guaranteed to be ruined by something.
The trade-off in how many / how long subexposures to take has been analyzed and discussed to death by astro imagers. To cite a few videos I enjoyed: https://www.youtube.com/results?search_query=astrophotograph... , https://www.youtube.com/watch?v=T_k9B01AeFM , https://www.youtube.com/playlist?list=PLaDi49CzWbrYhWEKxWiwB... , https://www.youtube.com/watch?v=mj5zn_Jz3dE , https://www.youtube.com/watch?v=n1RbyswFUqs
As for ISO, it is very commonly misunderstood. ISO amplifies photon noise and dark current noise, and changing the ISO doesn't make your images better or worse in these aspects. ISO in the form of analog gain can help boost the signal above the analog-to-digital converter noise, and that's what it's useful for. The MinutePhysics video explains excellently: https://www.youtube.com/watch?v=ZWSvHBG7X0w . More and more sensors these days approach "ISO invariance", where analog amplifier gain has about the same effect as digital gain (i.e. multiplying the measured numbers on a computer).
Exactly what I'm refuting:
> exposure duration
In astronomy, more is better. Get as much total exposure time as you can afford (e.g. time being at a suitable location, time spent monitoring the equipment, time under clear skies).
> aperture
In astronomy, more is better. Buy the biggest aperture you can afford - obviously, subject to constraints such as cost, weight, mountability, focal length. Also, telescopes don't have adjustable aperture blades, unlike general photographic lenses. You could put a disc cut-out in front of the telescope to close down the aperture, but that's just a waste of light.
> minimum amount of sensor noise
You get the least amount of sensor noise by reducing the exposure time and reducing the temperature (dedicated astro cameras have Peltier cooling). Note that although noise increases with time, signal increases with time faster, so the signal-to-noise ratio is proportional to the square root of time. So 100× more exposure time gives you a 10× better SNR.
> stacking the images typically gives better results than one massive exposure
This is the main falsehood that I wanted to address. Taking multiple images actually gives more noise overall, even if it's a tiny bit. But multiple images gives you much more processing flexibility and the ability to selectively reject things.
Exposure time (in digital imaging) is directly related to sensor well saturation.
It does not mater how much water you pour into a full bucket.
Do iPhones count?
I've taken multi-hour continuous exposures on my iPhone + iPad (both "normal" and "light trail" variants.)
By the looks of [0], you can do at least 90 seconds on the Olympus E-M5 MK II - which is what I have and I'll see if it can do 10 minutes tonight.
[0] https://www.olympuspassion.com/2019/08/26/long-exposures-wit...
My Canon can do this without modification and its 8 years old. Switch to bulp and have an external mini device which you connect with a microphone cable and it creates the signal for shutter off after x minutes.
For extra long exposre its recommended to use also a stable powersource.
How is a 10 minute continuous exposure functionally different from 10 minutes of video with every frame stacked? In the former, each photodiode acts as a compositor for each pixel instead of whatever algorithm is chosen to combine frames in the latter?
You pay the read noise every time you read out the sensor and digitize the values. Also, you lose a tiny bit of time between exposures as the sensor resets itself. And you might have a bottleneck in moving the data off the sensor and saving the image. Furthermore, if you perform lossy compression on the video, then your digitally stacked image will differ significantly from analog stacking on the silicon sensor.
Maybe, but also a lot of satellites rotate and so their brightness changes over time.
Passing clouds?
[dead]
I fear this is only the start of it. A minimum of 3-4 constellations more will probably be launched in the near future (Russia, China, EU).
Their obvious dual-use nature makes them tempting, and a military target if a large conflict will take place in the near future. I hope their lower orbit will help any space junk burn up fast.
Add a black umbrella to each satellite: when they pass through the critical region where they are visible in the night sky while still being sunlit, pop the brollies up. We will fly them in the shade!
You could paint them black but they’d probably get quite hot.
Won't the shade then reflect the light instead? It's nighttime, so sunlight will be aimed up, from the Earth-based observer's point of view, so the shade will need to be pointed down in order to shade the satellite.
If you blow up a satellite, half of it will end up going slower and half will go faster. The slower bits will probably burn up nicely, but the faster bits will just elevate their orbit.
I doubt they will elevate their orbit by enough to be a problem. Some bits will come down in hours, some will come down in a year - even in the worst case where it takes out everything in low earth orbit in 5 years everything will be clear and we can start over. Higher orbits are the real worry, even the things slowed down mostly stay in orbit for centuries - but higher orbits are mostly a lot higher.
Don't be so sure: https://stuffin-space.vader.zone/
The Iridium-Kosmos collision fragments have been up there since 2009, and that's a massive spray of junk just from one disintegration in LEO.
"LEO" is a big place, those satellites collided ~1.5x higher than e.g. the maximum Starlink altitude and the debris lifetime relationship is not a linear one.
It'll elongate the orbit, which is a bit better of a scenario than elevating it wholesale.
In either case, you will increase the section area / volume ratio, what makes the fragments fall from LEO faster.
[dead]
FWIW, if you actually want to photograph a comet or anything that doesn’t move in the sky, you’d take multiple exposures that would make the moving light sources like satellites disappear. Taking HDR photographs like this has an number other benefits as well.
I'm rebuilding my RSS feed collection, and having pretty astronomy pictures is a fine addition. Thanks!
So cool! Zoom in to find out: https://zoomhub.net/0w8pN
I, a taxpayer, would rather have a cellphone signal in a remote location than lots of amazing pictures of a comet. And I just don't see a solution or compromise that could work. The utility of neat picture vs full cell signal in a Montana canyon cannot be won by taking more pictures and showing me the problem. I made my decision already.
I, a taxpayer, wish that we could significantly reduce light pollution so we could see the stars on a typical clear night.
Then give up streetlights. Although crime and road accidents will massively increase and women won’t feel safe outdoors. So is it really worth it?
We don't need to give up streetlights to make huge progress. 20 to 50 percent of outdoor lighting is wasted. Just shielding streetlights would go a long way.
https://www.nps.gov/subjects/nightskies/sources.htm
Women would feel less safe yes but there is no evidence that crime and road accidents would increase.
Why gaze up at the vast cosmos when we can stare down at a little screen
Why have cheap radio safety when you can die under the stars?
How is it relevant that you're a taxpayer?
https://www.cnbc.com/2020/12/07/spacex-starlink-wins-nearly-...
Well, isn't that good for you? The other seven and a half billion of us just get to deal with having our skies skidmarked like this with no choice on the matter.
You can use satellite Internet too.
It's strange to call it "skid marked" when the "skid marks" only appear when you apply complicated technology setups, and those setups can easily remove the "skid marks" also.
"Now, the orbiting satellites themselves only appear as streaks because of the long camera exposure, over 10 minutes in this case. On the contrary, to the eye, satellites appear as points that drift slowly across the night sky and shine by reflecting sunlight -- primarily just after sunset and before sunrise. "
See https://apod.nasa.gov/apod/ap191014.html for example
I , as a citicen, would like that research will figure out the origins of space and time
"As an American, I believe that my personal convenience outweigh the needs and desires of literally every other person on the entire planet"
> can you find the comet?
You mean the obvious object (ball shaped head with a tail) in the center of the image?
That was super hard.
Why doesn't the comet "streak" also, given the Earth's rotation? 10 minutes is a long enough window to have an appreciable impact on the comet's image. Or is it the case that the telescope is stabilized to the Earth's rotation?
Low earth orbit satellites orbit about once per 90 minutes, so in 10 minutes they go about 40 degrees across the sky. The comet is not even orbiting the earth, it's essentially fixed in the sky. The earth only rotates about 2.5 degrees in 10 minutes. So the satellites streak is 16 times longer than the comets.
> essentially fixed in the sky
Let's start with "fixed in the sky" and qualify your frame of reference as the field of distant stars, or the celestial sphere. The common coordinate system is right ascension (RA) and declination (dec).
The GP question was about the Earth's rotation, which would be in terms of azimuth and altitude, and that question's been asked and answered. The key terms there: "equatorial mount" and "clock drive".
The comet C/2025 R3 (PanSTARRS) is in fact near its highest velocity (with reference to the Sun especially), being near perihelion while this photograph was taken. The comet is swinging around the Sun, and it was about 0.49 AU from Earth at the time of the photograph.
https://en.wikipedia.org/wiki/C/2025_R3_(PanSTARRS)
I chose an approximate time on April 27: in 10 minutes of wall-clock time, with the J2000 epoch, the comet's apparent motion is from RA 02h 49m 07.1s, dec +06° 02' 56.5" to RA 02h 49m 15.4s, dec +06° 02' 13.3"
That is a distance of 2' 11.13" across the celestial sphere. For reference, Venus is 11.6" wide in the sky as we see it this week.
24 hours later, we find it at RA 3h 08m 44.1s, dec +04° 19' 27.8". Its apparent motion was 5° 10' 46.02", which is approximately the width of your three middle fingers held together, at arm's length.
So, "fixed in the sky" is not a scientifically useful description of astronomical objects: we need to put that in terms of at least one frame of reference, and "apparent motion" which is how an observer perceives it.
https://soho.nascom.nasa.gov/data/LATEST/latest-lascoC3.html (grab this today; scroll between 4/23 and 4/27)
Given that the moon is about 0.5 degrees in diameter from Earth, shouldn't we expect to see the stars and comet much more blurred than they are here though? Or the ground if it's stabilized against the rotation?
40 degrees around Earth (central angle)
but it increases to much more when you are much closer to the arc
Great point!
https://www.facebook.com/groups/Nachtfotografie/posts/264063... Here is the original photo description in German. See also my other comment in this thread. But the tl;dr is that this was a stack of 153 four-second exposures with some gaps in the timelime when the camera took its time to save between exposures.
Finding the comet among those trails is a fun challenge. It's amazing how much detail can be captured in a long exposure like that.
Is this all / mostly Starlink?
It's a set of network satellites for sure either by Eutelsat or Starlink in 70:20 ratio 10% being other providers
But all of them being LEO for sure.
70% of all satellites are Starlink. So probably.
if i could imagine what a Sophon from 3 body problem would look like. this is kind of it.
Hot take: We're in the first stages of building our own Dyson sphere and therefore comets are only useful in the context of capturing them for that purpose.
;)
The idea of a Dyson sphere is that it's built around a star, in attempting to capture and utilize 100% of its energy output. So a shady shell around the Earth is not "the first stages" of a Dyson sphere, because our energy source is on the other side of the shell, and the orbits are completely different.
We do not need Starlink! It only provides service to 9 Million! People
We are a planet with 8 Billion People.
Do i want cheap and reliable internet everywhere and perhaps work remote? Yes. Should someone like Musk destroy our look into space for just me and my use case? No.
I do wonder if in 100 or 200 years if we do become interplanetary as a species, and technology advances if many of these satellites will just disappear from the night sky and it would be long since forgotten or if remembered only as a steppingstone towards an interplanetary future.
In the meantime, Starlink is the only thing that gives my sister in Puerto Rico access to the internet when the grid gets completely nerfed by a hurriance so she can tell us she's alright, well, that and landlines if she gets a power generator, otherwise, we're left to wonder how my sister and nephews are doing.
You don't need starlink to get a message out of Puerto Rico.
We also don't need starlink as a stepping stone.
What we need is food for the planet, resiliance infrastructure, proper health care, stable energy grids.
I sure hope you never have to wonder if your relatives are safe and doing well after they have no way to communicate with you for weeks.
1. to keep this argument properly, you still need to see what the overall benefit for the whole society is and not just your little bubble. And putting a lot of satelites in sky, affects 8 billion people.
2. As i said, robust infrastructure would fix that too. Fiber under earth, backup energy etc.
Not to play the musk’s advocate, but there is a case to be made that proving internet access in remote places is more valuable than a perfect night sky. If you live in the cities you can barely see the stars anyway, so you’re not missing much. But in an austere environment, connectivity can be the difference between life and death. It also lowers the bar, encouraging more people to visit wild places and make them more likely to support their protection in more meaningful ways.
Speaking as someone comfortable with the outback night sky I'm fine without it thanks. So are pretty much all the locals and traditional owners of the Murchison Quiet Zone which is focused more toward radio silence overhead for SKA and such things .. so that all dovetails together.
If you're relying on starlink via a smartphone, you're basically unprepared in any case.
Nice to have, better to be better prepared.
Yeah just that these satelites are not geostationary. They have to fly around. So its either all or nothing.
And People survived fine without Starlink
It is obvious that the 9 million current customers are just the beginning of where SpaceX wants to take Starlink access. Easy to imagine Starlink serving 1 billion + customers in the near future.
Its already quite cheap so why are people are not running to Starlink?
Probably because a land line has still less latency, doesn't consume that much energy and everyone has either a land line or mobile connection.
When Amazon Leo, Eutelsat, Telesat, Chiense and co enter the market, the margin will go down significanlty. The effort for handling the space and crashes etc. will increase.
Additional to this, my landline is stable. Its stable in heavy rain, with and without snow.
And the worst thing about Starlink and its adoption is the Satelite handoff every 15 seconds. I tried Starlink at my father-in-laws home and i was unable to use MS Teams reliable enough.
To finish Starlink off: it doesn't even properly scale. Right now they need v3 which they are not sending up because of the bandwidth limitation of one satelite. Then they have to route traffic through their satelites to were they have base stations. Now they also need to build basestations everywere together with sending up new satelites every 5 years.
1 billion customers? in that market? in the near future? never. The base stations we have are there, well connected, relativly cheap, very fast, very direct.
I've had no issue with starlink when using it at a friend's house, and I would be happy to use it myself if my internet provider decided to charge me more than what Starlink costs. And fiber has its own costs to install and maintain. A lot depends on the economies of scale for both systems, but to think that base station capacity and kessler syndrome fears are insurmountable obstacles is ridiculous.
To me, this is no different than the adoption of mobile phones: "Cell phone usage will never overtake landlines, we'll never fix the problems of bandwidth and cell phone towers that need to be installed everywhere. Sure there might be a market for a few million in the US but no more than that".
For me its a night sky and astrophotography issue.
https://www.space.com/space-exploration/international-space-...
https://www.chosun.com/english/industry-en/2025/12/11/55MMV2...
And Starlink, Amazon, China, etc. and co want to send up A LOT more.
As others have mentioned in the thread, the narrow impediments to some night sky photography affect a much smaller portion of the population compared to the benefits these satellites already provide. Returning to the cell phone example, would be like opposing cell phone towers for impeding wildlife photography.
How many hours are spent looking at the sky compared to Starlink usage?
Puh i would say a billion to 1? Like i look at the sky very often but i do not use Starlink.
My wife enjoys sun rises and sun downs.
Culture wise I know plenty of people around me looking up.
How about you?
Are you or people around you do that for hours every night? Is this a deliberate activity, or are you including random quick glances? How often is yours or people's around you sky watching experience actually negatively affected by satellites?
Sun rises and downs is not affected by satellites, due to overwhelming brightness difference. For casual stargazers, light pollution is much more of an obstacle than the satellites. Plus, for half a day on average, the stars not available at all, unlike Starlink or other satellite services
I'm not a Starlink user either, I do like to look at the sky with naked eyes and telescopes, but I do not share the sentiment that it's imperative to keep it "pure" for the sake of whatever. Also, a personal anecdote, satellite spotting is quite fun :)
I think its a fundmanetal human thing to look in the night sky. It swhat anyone did before us.
I also enjoy doing astrophotography, I want to build my own mirror.
People around me do this too yes.
That looks so cool, ngl!