  The brightness of the moonless night sky above La Palma was measured on 427
CCD images taken with the Isaac Newton and Jacobus Kapteyn Telescopes on 63
nights during 1987 - 1996. The median sky brightness at high elevation, high
galactic latitude and high ecliptic latitude, at sunspot minimum, is B = 22.7,
V = 21.9, R = 21.0, similar to that at other dark sites. The main contributions
to sky brightness are airglow and zodiacal light. The sky is brighter at low
ecliptic latitude (by 0.4 mag); at solar maximum (by 0.4 mag); and at high
airmass (0.25 mag brighter at airmass 1.5). Light pollution (line + continuum)
contributes < 0.03 mag in U, approximately 0.02 mag in B, approximately 0.10
mag in V, approximately and 0.10 mag in R at the zenith.
  This paper is a summary of results which are presented in full elsewhere
(Benn & Ellison 1998, La Palma Technical Note 115).

Astrophysics