Sky brightness measurements for different environmental conditions by the example of St. Petersburg

St. Petersburg is unique place in Russia with an environmental phenomenon called “white nights” during summertime: sky brightness levels are influenced mostly by environmental conditions. Sky conditions during the winter are opposite: light emission is mostly caused by the anthropogenic factors. A series of experiments were conducted between May and December 2017 using a Sky Quality Meter (SQM-LU-DL), a night sky brightness photometer, to understand the differences between sky brightness levels for different environmental conditions and seasonal variations. Sky brightness distinction between the city center and 20 km distance were estimated for clear sky conditions