Average values are given of the night sky brightness observed with visual photometers in Brazil, Bikini, Maryland, and New York State, which covered latitudes from 17° south to 45° north. The measurements revealed no important variations with latitude. For clear air, no moon, and noaurorae the brightness decreased on the average from about 225 millimicrolamberts at 15° above the horizon to 130 at the zenith. Previous determinations of the height of the night sky luminosity by means of the observed curves of brightness against zenith angle have lead to conflicting results, values from 60 to more than 500 km being reported. When the determination was repeated with recent data and with the improved corrections of Piotrowski for atmospheric attenuation and scattering such discrepancies between theory and experiment appeared that no certain values of the height were obtained.
E. O. HULBURT, "Night Sky Brightness Measurements in Latitudes below 45°," J. Opt. Soc. Am. 39, 211-214 (1949)