Can You Find the Comet?
apod.nasa.gov
apod.nasa.gov
(telescopes in space looking outside should have happened long ago, lets just get it done man)
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.
[0] https://doi.org/10.1109/AERO50100.2021.9438165
[1] https://en.wikipedia.org/wiki/Lunar_Crater_Radio_Telescope
There are some classes of observatories, which you cannot build in space but which are still affected by satellites to some degree.
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?
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
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.
The limiting factor of passive optical telescopes on earth is the atmosphere.
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.
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).
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.
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?
A small telescope is just a small telescope even when you put it in space.
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.
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.
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.
And with 9 million customers its not.
It reduces the signal-to-noise ratio of the image, making more difficult the detection of faint objects.
Compared to the processing already done to get data from astronomical data, yeah, it's essentially free.
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.
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.
More satellites means higher risk on that happening and not going to space until all the debris of a collision deorbits.
Is the camera exposure taking a few seconds of break between takes that get stacked later with some "missing" moments in between?
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...
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.
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.
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.
It does not mater how much water you pour into a full bucket.
For extra long exposre its recommended to use also a stable powersource.
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.
Here is a link to the original photo and it's description (German) by Uli Fehr: https://www.facebook.com/groups/Nachtfotografie/posts/264063...
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.
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.
You could paint them black but they’d probably get quite hot.
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
You mean the obvious object (ball shaped head with a tail) in the center of the image?
That was super hard.
but it increases to much more when you are much closer to the arc
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)
But all of them being LEO for sure.
;)
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.
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.
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.
2. As i said, robust infrastructure would fix that too. Fiber under earth, backup energy etc.
And People survived fine without Starlink
If you're relying on starlink via a smartphone, you're basically unprepared in any case.
Nice to have, better to be better prepared.
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.
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".
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.
My wife enjoys sun rises and sun downs.
Culture wise I know plenty of people around me looking up.
How about you?
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 also enjoy doing astrophotography, I want to build my own mirror.
People around me do this too yes.