As he pointed out later (“After sunset or before sunrise while the sky is dark is the best time to see them“), the lower satellites are only visible for a short time — maybe an hour-ish on either side of nighttime. It is the higher satellites that will streak across the sky while taking long exposures later in the night. Geostationary satellites would be among the worst (as well as those in its “graveyard” orbit, a couple hundred kilometers above geostationary orbit).

The geostationary satellites are in shadow for only about an hour-ish each night, so that gives you a maximum amount of exposure time, for certain areas of the sky, depending upon your latitude. Of course, the wider your field of view, the shorter time you have for your exposures before these satellites start to infringe on your exposure.

Even long exposures of higher latitude stars can end up with satellite streaks. Some orbits, especially highly elliptical orbits, can keep satellites lit by the sun for long periods of time. The Molniya orbit and Tundra orbit (an example of a geosynchronous orbit that is not over the equator) put satellites in high inclination orbits that allow them to “hover” over parts of the Earth for several hours. Sun-synchronous can put a satellite in constant sunlight, because the plane of that orbit precesses at the same rate that the Earth orbits the sun.

This discussion is giving me renewed appreciation for the decision to put the James Webb Space Telescope in the Earth-Sun L2 location, far from Earth-orbiting satellites.

* Satellite orbits change due to the effect of the shape of the Earth. When you calculated orbits in high school, you assumed a point source for gravity, and a spherical, evenly dense planet or star would act that way. But the Earth is not spherical (e.g. Earth has mountains) and density changes (e.g. oceans are less dense than land).

Think of a satellite passing almost over a mountian that juts up almost to the satellite’s orbit. If the mountain is on the left side of the satellite’s orbit, then the difference in gravitational pull would make the satellite turn slightly to the left, and after it passed the mountain, it’s orbital plane would have changed.

Because it spins, the Earth “bulges” at the equator, so it has a very mild out-of-round shape, ever so slightly like M&Ms or Reese’s Pieces. The effect is similar to the Earth having a 3-mile high mountain range around the equator.
https://en.wikipedia.org/wiki/Nodal_precession

I see satellites cross the view of my eyepiece on a regular basis now. Many are so small I can’t see them naked eye, but a camera would pick them up.

If you live in a place without excess light pollution, spend a half hour or so looking up and you’ll start seeing them. After sunset or before sunrise while the sky is dark is the best time to see them. Remember, you have to be in the dark, while the satellite is lit by the sun.

Tom Billings, It will still cost $40 million or so to launch anything to orbit, even with SPX reusability. A 2 meter mirror sounds heavy. But if they don’t have the ambition to do new kind of science, just increase the amount of observations, I suppose such telescopes could be made much more cheaply than the unique instruments at the frontier of engineering that astronomers prefer.

Most amateurs do it with their own equipment simply for the challenge of it.

Of course, the same capabilities that will put all these LEO comsats in place can also put in slightly higher orbits *really* cheap 2 meter mirror telescopes (spinning furnaces for mirrors can churn them out) for small groups and even individuals. It will *shift*the*place* from which astrophotography is done by 2030, and may actually make it more popular.

I guess I’m glad that I’m just a visual observer. The Astro-Photographers are going to be cursing all of the ruined shots they’re going to have to deal with…