The BlackGEM Twilight Survey (BG-Twilight)
Every twilight there is a window of half an hour where the skies are too bright for deep Universe observations but too dark for calibration images. This is the time when the BlackGEM Twilight survey will be performed to monitor a set of nearby (<30 Mpc) large galaxies in two filters (u and r). The scientific aim is to monitor the population of massive, luminous binary stars in the nearby Universe, and to detect low-luminosity transient events.
Per twilight 39 fields, each 2.7 square degrees large, will be monitored. Each field will be revisited every day for as long as it remains visible to the array.