Major observatories schedule their whole year around the Moon. The nights near new moon are called dark time, and astronomers fight over them.

Telescope committees split the calendar into bright, grey and dark time by lunar phase. Faint galaxies and distant supernovae need the darkest nights, so those hours go to the most competitive proposals; planets and bright stars get the moonlit ones. The Moon is the largest source of light pollution in the sky and it is the one nobody can switch off.