One night around 8pm I was attending the outdoor portion of my astronomy lab and calibrating the telescope. Most of the class was inside still finishing the pre work and my team members were focused on the settings of the telescope and not particularly paying attention to anything else. The campus was lit up though no lights were on our roof to help keep our vision adjusted and I glanced up to for a minute while the others finished setup. I just barely noticed a shadow, darker than the rest of the night sky. It was moving quickly and silently in a straight line with no illumination of any sort. I cannot guess a size or distance as there was no details or range to compare it to, it was shaped like a smoothed boomerang with slight triangular stripes on the leading edge of the wing that were just a shade lighter than the rest of it. I thought about trying to point it out to the others but I could still barely see it and I doubted I could draw their attention to it in time before it passed us; besides I was sure it was something explainable and didn't want to be the UFO guy to them lol. I love aerospace and aviation and I assumed I could find an explanation but the more I thought on it the more I failed to answer what it was with any conventual logic. I do not believe in extra-terrestrial visitors but my only actual guess is someone had flown a massive glider, fairly high up, in pitch black night, with no lights and with no where to launch from nearby. This infuriates me that I have never found an explanation, hopefully someone can solve this where I couldn't.