UBVRI night sky brightness at Kottamia Astronomical Observatory

Area of Science:

• Astronomy and Astrophysics
• Atmospheric Science
• Environmental Science

Background:

• Night sky brightness (NSB) is a critical factor for astronomical observations.
• Urban development can significantly increase light pollution, affecting astronomical sites.
• The Kottamia Astronomical Observatory (KAO) in Egypt is experiencing potential impacts from nearby urban expansion.

Purpose of the Study:

• To measure and characterize the night sky brightness at KAO using the UBVRI photometric system.
• To assess the impact of new urban development on the sky glow at KAO.
• To determine the effects of light pollution on astronomical observations conducted at KAO.

Main Methods:

• Conducted photoelectric observations of NSB at various zenith distances and azimuths at KAO.
• Utilized a fully automated photoelectric photometer (FAPP) with the Bessel UBVRI filter system.
• Collected data over three consecutive nights (August 1-3, 2022) under optimal atmospheric conditions.

Main Results:

• Average zenith sky brightness values were determined for U, B, V, R, and I filters (20.49, 20.38, 19.41, 18.60, 17.94 mag/arcsec²).
• Average zenith color indices (U-B, B-V, V-R, R-I) were measured (0.11, 0.98, 0.81, 0.66).
• Isophotes of sky brightness were plotted, and atmospheric extinction and transparency were calculated.

Conclusions:

• The study quantifies the current NSB levels at KAO, providing a baseline for future monitoring.
• Results indicate a significant impact of newly developed cities surrounding KAO on sky glow.
• The observed light pollution levels are likely to affect various types of astronomical observations.