Astronomical observations are naturally very sensitive to light pollution, which is why you typically place observatories in desolate locations. Even there, you are not guaranteed success, as someone may turn on the light in the dome, shine a flashlight towards the telescope etc. meaning that your observations will be ruined.

Young George Coyne was observing at the Vatican Observatory in Castle Gandolfo, when someone opened the door to the observatory and let in a lot of light, ruining the exposure. George shouted “close that bloody door”, after which the visitor promptly vanished, closing the door behind him. George then continued his observations for the remainder of the night, without further interruptions.

The following day, Pope Paul VI reminded him “my son, you should be in better control of your temper.”

Guess you never know who might be popping by the observatory at night…