<p>Tl;dr, From personal experience, it’s not worth it. It’s a lot easier to throw away bad data than to try to calculate when stop. There’s not a lot of ambiguity as to whether it messes up the data.</p>
<p>As of right now, it’s not that big a problem either. Sure, some are particularly unlucky, as seen with a Magellanic cloud observation in early 2020. The concern is more the future: 12,000+ satellites (that are unusually bright compared to similar satellites) could cause problems in the future, for not only observational astronomers, but for the amateur observer’s night sky; just like telephone lines would ruin natural views, the fear is that too many satellites would do the same to our night skies.</p>
<p>There are other concerns as well, but what it boils down to is a lack of a way to deal with it. Right now, the occasional satellite coming into view messes up a frame or two of data, you consider it an unlucky break, and you move on with one less data point. There may be some state of the art observatories that consider whether a satellite will cross their observational area at night, but I have never worked at one that does. And that’s because it just isn’t worth it for how frequent a problem it is. Space is big; sometimes the area you’re looking at is really small, and between those two you’re normally OK for the most part.</p>
<p>To my knowledge, no (commonly used at least) archive possesses a collection of all satellites from all the different entities (government, businesses) and where they’ll be. Sure this information is accessible, but there’s quite a few entities on the Earth that have satellites in the sky; to have all of their info in the same place is a major undertaking. Now there may be some versions of this for those looking to put new satellites in space, regarding orbits etc, but there is not a tool that I’m aware of that has relevant tools for observational astronomers.</p>
<p>And right now we don’t need that. And honestly it’s a lot easier to toss out bad data than to try to weave intermediate stops into your tracking program for your telescope. But maybe some day we’ll have to plan observations so that we don’t waste too much valuable telescope time on bad data. Time will tell.</p>

CC BY-SA 4.0
2021-09-14T07:19:01.933Z
Can the 'bad data' be restored to some point, when it is really necessary? For instance, filtering out the satellites?
Thank you.
Lariliss
CC BY-SA 4.0
2021-09-14T07:39:31.273Z
It unfortunately can be difficult to do that. When you’re taking data, you’re observation is tailored to the object you’re looking at. Look at it too long, or next to something too bright in comparison to your object, the CCD (the thing collecting photons from the sky) becomes saturated, resulting in a loss of information. On top of that, depending what kind of observations you’re doing, you might be averaging several pictures into one, and some bad data points or, conversely, a lack of data points would mess up your average. The approach and difficulty can depend greatly on what youre doing
Justin T
CC BY-SA 4.0
2021-09-14T15:46:20.513Z
"But maybe some day we’ll have to plan observations so that we don’t waste too much valuable telescope time on bad data" - but in the meantime, I would expect there to be more satellites and therefore more of a problem, rather than less. :(
Don Branson
CC BY-SA 4.0
2021-09-14T23:07:51.203Z
The solution is to make Musk feel so guilty he starts launching orbital telescopes for you.. If you plan this right you might even get an orbital _observatory_ and rides to and from.
Peter Wone
CC BY-SA 4.0
2021-09-14T23:47:26.100Z
Norad has them all. Too bad we can't tap it.
Joshua
CC BY-SA 4.0
2021-09-15T21:55:33.140Z
Note that 4 pi steradians divided by $\sqrt(12\,000)$ satellites gives a mean spacing of less than 10 mrad (about 1/2 a degree) between the satellites (when viewed from the center of the Earth)...  This means, for random instance, the VISTA telescope will essentially always have one or more such satellites in its field of view (when pointed in their [orbital band](https://en.wikipedia.org/wiki/Starlink#/media/File:Starlink_SpaceX_1584_satellites_72_Planes_22each.png) (That image is an orbital picture for just the first <2000 satellites.)).
Eric Towers
CC BY-SA 4.0
2021-09-16T05:21:47.653Z
https://www.n2yo.com/satellites/ and https://www.satflare.com/search.asp seem to have a pretty thorough tracking database that aims to be fairly comprehensive using NORAD numbering.
JeopardyTempest
CC BY-SA 4.0
2021-09-16T06:18:35.610Z
While those websites are good for tracking individual websites, the first only gives location predictions out to 10 hours, and the latter is only capable of tracking one satellite at a time. So while a step in the right direction, the most useful type of tool for an observational astronomers would have the means of predicting satellite trajectories for at least up to a couple years in advance (some types of observations, like transiting planets, are planned this far in advance because of extremely long periods) for a given search radius, telling you if a satellite would cross your image then.
Justin T
CC BY-SA 4.0
2021-09-16T07:09:21.670Z
@user253751 yes but can't you stop recording all the photons for a few seconds? By obstructing the sensor for example.
Alexis Delrieu
CC BY-SA 4.0
2021-09-16T07:41:37.540Z
@Alexis Delrieu Like mentioned in the answer, its more about timing and what a hassle that is than the action of actually turning off the sensor. In fact, turning it off risks missing data right before or after the satellite passes, it is much easier to throw away bad data then to time it and turn it off.
Justin T
CC BY-SA 4.0
2021-09-16T23:01:53.167Z
@JustinTackett indeed.  But shows they're out there, both the database of satellites and with the information to do calculations (no idea how precise they are though).  So if they're any good, they should be able to get ahold of it, if nothing else, for a price (shouldn't imagine too much).  I agree with the general idea that it's probably usually easier to just remove the data that's obscured, but wouldn't be a surprised on like long exposure imagery to see the calculations planned around more as time goes on, or even the concept Alexis proposes used in certain specialized situations.
JeopardyTempest
CC BY-SA 4.0
2021-09-17T16:22:58.287Z
@JeopardyTempest I completely agree that the information is out there, even in more details I’m sure in other locations because people need to plan their own satellite trajectories and need to make sure they won’t interrupt another satellite’s orbit, but the key here is accessibility for observational purposes. Without things like searching based off of an area of the sky instead of by satellite, it’s not accessible in a way that’s particularly useful. That being said, I have no doubt soon this will be no longer the case, if it isn’t already with some other program or website.
Justin T
CC BY-SA 4.0
2021-09-14T06:44:44.077Z
2021-09-16T00:04:29.623Z
2021-09-16T00:04:29.623Z
Justin T
<p>Given that the positions and trajectories of the Starlink satellites are public, why can't the telescopes just ignore the photons they receive when the satellites pass through the field of view?</p>
<p>It seems that they could &quot;just&quot; stop image capture for a few seconds before and restart a few seconds after.</p>
<p>Is it that simple, or are there other complicating factors?</p>

CC BY-SA 4.0
2021-09-14T08:53:03.193Z
See also https://astronomy.stackexchange.com/questions/43474/will-starlink-deface-the-night-sky
henning no longer feeds AI
<observational-astronomy><artificial-satellite><observatory><deep-sky-observing>
Why can't observatories just stop capturing for a few seconds when Starlink satellites pass though their field of view?
Alexis Delrieu
# Why can't observatories just stop capturing for a few seconds when Starlink satellites pass though their field of view?

(Asked by: username_0 on 2021-09-13)

Given that the positions and trajectories of the Starlink satellites are public, why can't the telescopes just ignore the photons they receive when the satellites pass through the field of view?

It seems that they could "just" stop image capture for a few seconds before and restart a few seconds after.

Is it that simple, or are there other complicating factors?

**Tags:** observational-astronomy, artificial-satellite, observatory, deep-sky-observing

> **Comments:**
> **username_1**: See also https://astronomy.stackexchange.com/questions/43474/will-starlink-deface-the-night-sky  

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## 1 answers

### Answer by username_2 on 2021-09-14. Score: 30

Tl;dr, From personal experience, it’s not worth it. It’s a lot easier to throw away bad data than to try to calculate when stop. There’s not a lot of ambiguity as to whether it messes up the data.

As of right now, it’s not that big a problem either. Sure, some are particularly unlucky, as seen with a Magellanic cloud observation in early 2020. The concern is more the future: 12,000+ satellites (that are unusually bright compared to similar satellites) could cause problems in the future, for not only observational astronomers, but for the amateur observer’s night sky; just like telephone lines would ruin natural views, the fear is that too many satellites would do the same to our night skies.

There are other concerns as well, but what it boils down to is a lack of a way to deal with it. Right now, the occasional satellite coming into view messes up a frame or two of data, you consider it an unlucky break, and you move on with one less data point. There may be some state of the art observatories that consider whether a satellite will cross their observational area at night, but I have never worked at one that does. And that’s because it just isn’t worth it for how frequent a problem it is. Space is big; sometimes the area you’re looking at is really small, and between those two you’re normally OK for the most part.

To my knowledge, no (commonly used at least) archive possesses a collection of all satellites from all the different entities (government, businesses) and where they’ll be. Sure this information is accessible, but there’s quite a few entities on the Earth that have satellites in the sky; to have all of their info in the same place is a major undertaking. Now there may be some versions of this for those looking to put new satellites in space, regarding orbits etc, but there is not a tool that I’m aware of that has relevant tools for observational astronomers.

And right now we don’t need that. And honestly it’s a lot easier to toss out bad data than to try to weave intermediate stops into your tracking program for your telescope. But maybe some day we’ll have to plan observations so that we don’t waste too much valuable telescope time on bad data. Time will tell.

> **Comments:**
> **username_3**: Can the 'bad data' be restored to some point, when it is really necessary? For instance, filtering out the satellites? Thank you.  
> **username_2**: It unfortunately can be difficult to do that. When you’re taking data, you’re observation is tailored to the object you’re looking at. Look at it too long, or next to something too bright in comparison to your object, the CCD (the thing collecting photons from the sky) becomes saturated, resulting in a loss of information. On top of that, depending what kind of observations you’re doing, you might be averaging several pictures into one, and some bad data points or, conversely, a lack of data points would mess up your average. The approach and difficulty can depend greatly on what youre doing  
> **username_4**: "But maybe some day we’ll have to plan observations so that we don’t waste too much valuable telescope time on bad data" - but in the meantime, I would expect there to be more satellites and therefore more of a problem, rather than less. :(  
> **username_5**: The solution is to make Musk feel so guilty he starts launching orbital telescopes for you.. If you plan this right you might even get an orbital _observatory_ and rides to and from.  
> **username_6**: Norad has them all. Too bad we can't tap it.  
> **username_7**: Note that 4 pi steradians divided by $\sqrt(12\,000)$ satellites gives a mean spacing of less than 10 mrad (about 1/2 a degree) between the satellites (when viewed from the center of the Earth)...  This means, for random instance, the VISTA telescope will essentially always have one or more such satellites in its field of view (when pointed in their [orbital band](https://en.wikipedia.org/wiki/Starlink#/media/File:Starlink_SpaceX_1584_satellites_72_Planes_22each.png) (That image is an orbital picture for just the first <2000 satellites.)).  
> **username_8**: https://www.n2yo.com/satellites/ and https://www.satflare.com/search.asp seem to have a pretty thorough tracking database that aims to be fairly comprehensive using NORAD numbering.  
> **username_2**: While those websites are good for tracking individual websites, the first only gives location predictions out to 10 hours, and the latter is only capable of tracking one satellite at a time. So while a step in the right direction, the most useful type of tool for an observational astronomers would have the means of predicting satellite trajectories for at least up to a couple years in advance (some types of observations, like transiting planets, are planned this far in advance because of extremely long periods) for a given search radius, telling you if a satellite would cross your image then.  
> **username_0**: @user253751 yes but can't you stop recording all the photons for a few seconds? By obstructing the sensor for example.  
> **username_2**: @username_0 Like mentioned in the answer, its more about timing and what a hassle that is than the action of actually turning off the sensor. In fact, turning it off risks missing data right before or after the satellite passes, it is much easier to throw away bad data then to time it and turn it off.  
> **username_8**: @JustinTackett indeed.  But shows they're out there, both the database of satellites and with the information to do calculations (no idea how precise they are though).  So if they're any good, they should be able to get ahold of it, if nothing else, for a price (shouldn't imagine too much).  I agree with the general idea that it's probably usually easier to just remove the data that's obscured, but wouldn't be a surprised on like long exposure imagery to see the calculations planned around more as time goes on, or even the concept Alexis proposes used in certain specialized situations.  
> **username_2**: @username_8 I completely agree that the information is out there, even in more details I’m sure in other locations because people need to plan their own satellite trajectories and need to make sure they won’t interrupt another satellite’s orbit, but the key here is accessibility for observational purposes. Without things like searching based off of an area of the sky instead of by satellite, it’s not accessible in a way that’s particularly useful. That being said, I have no doubt soon this will be no longer the case, if it isn’t already with some other program or website.  

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