With star trails, you wouldn't need to use night vision. Any obstructing objects would occlude a multitude of stars in a pattern that would jump off the screen.
The science of astrophoto analysis is, as Alex hints at, quite sophisticated. The process is often automated, analyzing thousands of photos at a time, and the faintest dots, moving a few pixels, sets off alarms. A whole group of stars disappearing for moments then reappearing, in a compact path, would be a riot of klaxons.
The advantage of this method is that we HAVE a dataset of such pictures going back decades by thousands of obsevers all over the world. That is far and away better than a few enthusiasts that can afford night vision goggles, going out on a few dozen nights and hoping they see something.
Why have UFOlogists not made the leap into the 21st century of "big data"?