I'm trying to do observations with my telescope from my apartment's balcony and I keep seeing more points of light moving fast across the night sky. A friend told me they're Starlink satellites and that they affect astronomers, but I don't quite understand how they exactly impact the images captured from observatories.
Starlink satellites reflect sunlight, and that creates bright streaks in photos taken by telescopes, especially in long exposures where they capture everything that happens over several seconds or minutes! It's like someone turned on a flashlight while you're trying to photograph something in the dark. For professional observatories it's a real mess because it ruins valuable scientific data, but from your balcony with a visual telescope (not a camera) you'd probably be less bothered because those little dots move fast and pass through without leaving a mark on your eye the way they do in long-exposure images.
Starlink's light pollution is especially annoying because those satellites are pretty close compared to other stuff in space, so they reflect a lot of sunlight even when it's already nighttime for us down here. If you want to do observations from your balcony, a practical option is to find a website or app that shows you in real time where the Starlink satellites are in your area - some of them alert you when they're going to pass over you - so you can avoid taking photos right at that moment.
Professional observatories have it tougher because their exposures last minutes or even hours, and in that time it's almost certain that some satellite will pass by leaving those white streaks that ruin the image. With your telescope from the balcony you have more flexibility to wait for them to pass, so take advantage of that.
What you're describing about seeing points moving fast is exactly that, and the impact on observations is pretty straightforward: when you take a long-exposure photo (say 30 seconds or more), the satellite passes through your field of view and leaves a bright streak that ruins that part of the image, especially if what you want to observe is right on that line. At professional observatories with more sensitive equipment the problem is even worse because they pick up more light, so even satellites that aren't visible to the naked eye can show up as annoying streaks. The frequency doesn't help either: there are thousands of these satellites in orbit already, so the probability of one crossing during your observation keeps getting higher, especially in the first and last hours of the night when the sky is dark but the satellites are still getting sunlight.
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