Sky Brightness Information

• Definition of dark/grey/bright time used by NOT OPC:
  7 nights centered on new moon (dark), 7 nights on full moon (bright) and grey the remaining nights.
• ING technical note 115: La Palma night-sky brightness
  Chris Benn (Isaac Newton Group) and Sara Ellison (Univ. of Kent), May 1998

  Darkest La Palma sky: U=22, B=22.7, V=21.9, R=21.0, I=20
  (high elevation, high ecliptic and galactic latitude, at sunspot minimum)
  Moonlight brightens the sky by about 1 mag (first/last quarter) to 4 mag (full moon) in UBV.
  In I the full moon brightens the sky about 2 mag.

• Estimated near IR sky brightness
  J=15-16, H=13-14, K=12-13