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Photoelectric observations of night sky brightness (NSB) at different zenithdistances and azimuths, covering all the sky, at the Egyptian KottamiaAstronomical observatory (KAO) site of coordinates {\phi} = 29{\deg}55.9'N and{\lambda} = 31{\deg}49.5' E, were done using a fully automated photoelectricphotometer (FAPP). The Bessel wide range system (UBVRI) is used for the firsttime to observe NSB for three consecutive nights (1 to 3 August, 2022) undergood seeing conditions after the moon sets. The deduced results were taken inphotons and converted into mag/arcsec2. The average zenith sky brightness forU, B, V, R and I filters are found to be 20.49, 20.38, 19.41, 18.60 and 17.94mag/arcsec2 respectively. The average color indices (U-B), (B-V), (V-R) and(R-I), at the zenith are detected to be 0.11, 0.98, 0.81 and 0.66,respectively. We plotted the isophotes of the sky brightness at KAO in U, B, V,R and I colors (filters) and determined both the average atmospheric extinctionand sky transparency through these UBVRI filters. The atmospheric and othermeteorological conditions were taken into our consideration during theobservational nights. The results of the current study illustrate the mainimpact of the new cities built around KAO on the sky glow over it, and whichastronomical observations are affected.

UBVRI night sky brightness at Kottamia Astronomical Observatory