UBVRI night sky brightness at Kottamia Astronomical Observatory

Abstract

Using a customized fully automatic photoelectric photometer, we measured the NSB in UBVRI filters at Kottamia Astronomical Observatory. The observations covered all the sky at all altitudes and azimuths with 10° steps at each. The observations were carried out on three nights of August, 1st, 2nd and 3rd 2022 and were averaged. The average zenith sky brightness is 20.49, 20.7, 19.34, 18.25 and 17.04 mag/arcsec2 in UBVRI filters respectively. The average color index is U-B = - 0.21, B-V = 1.37, V-R = 1.09 and R-I = 1.21 for the zenith. The average atmospheric extinction and sky transparency of the UBVRI filters were determined for the three nights of observations. We also included the atmospheric conditions during the observational nights.