So, you clear your CCD, collect photons for 30 minutes, then some satellite sprays you with a multiple of the number of photons collected thus far, and then ... what?
Instead of exposing for 30 minutes, astronomers take lots of shorter exposures and stack them. Otherwise you'd get tons of noise from CCD hot spots, cosmic rays, aircraft, meteors, satellites, etc.
Well, but then, you also get noise from CCD readout, so it's not like you can just take 18000 100ms exposures and stack them to get the same result as a 30 minute exposure minus the "broken frames". Stacking frames is a workaround for disturbances, but it comes at a cost in the form of readout noise. The shorter you make the exposures, the more disturbances you can filter out without wasting observing time, but the more readout noise you get. So, if you have more disturbances, you either need more telescope time so that you still have enough frames left to see your signal after you have thrown out all the bad frames, or you need to reduce exposure times so you can throw out frames as higher granularity, but then you have to accept more readout noise, which makes it harder to see the signal.
There are already enough disturbances that a 30 minute exposure is impractical. Astrophotographers tend to use exposures around 30 seconds. It's true that more satellites mean that astronomers will have to tweak their observation methods and/or reduce their observation windows, but it's not a showstopper. At worst it's an inconvenience to them.
If we were to employ the reversal test[1], the concern about astronomy would be a non-problem. Imagine if the entire planet was covered by the equivalent of 4G cell networks. And imagine if some astronomers asked us to destroy those networks so that some of their work could be made more convenient. Imagine all of the people affected by this network. All of the lives saved by emergency calls, all of the remote locations made digitally accessible to the rest of humanity, all of the scientific experiments in jungles, deserts, tundra… cameras and microphones and sensors reporting data through this global satellite network… imagine all of that destroyed so that some astronomers could be relieved of an inconvenience. That is absurd. Yet that is the world that some people want to live in.
It's so clear to anyone whose view isn't so parochial, so local in time and space, so blinkered by where and when they were born. Does anyone think that astronomers will still be preventing the launch of satellite constellations in the year 2100? In 2200? In 2500? Clearly not.
I'd rather the improvement happen in my lifetime than after. Launch away.
