  The level of the night sky background light at La Palma and Namibia was
determined, with emphasis on the wavelength region and solid angle coverage
relevant for the operation of imaging atmospheric Cherenkov telescopes. The
dependence of the night sky background light both on celestial coordinates
(alt, az) and on galactic coordinates (b, l) was measured, with an angular
resolution of about 1 degr. Average light levels near the zenith are similar in
both locations -- 2.2 x 10^12 to 2.6 x 10^12 photons per sr s m^2 for 300 nm <
lambda < 650 nm. With increasing zenith angle the level of background light
increases at La Palma, whereas a constant level is measured in Namibia. Near
the center of the Milky Way, background light levels are increased by a factor
up to 4 and more. Also the level of light backscattered from the ground has
been studied.
