Measurement and distribution of urban light pollution as day changes to night

Light pollution has a serious impact on astronomical observations and ecological balance. So far, most scholars have carried out field measurements of urban sky glow luminance using satellite data. However, measurement of the light environment of an entire city is insufficient. This paper presents measurements of the sky within the city of Dalian and examines the changes in the distribution of luminance and colour temperature of the sky. It was found that over the transition from day to night the colour temperature of the sky decreases by approximately 2000 K-3000 K and the light spectrum transforms from a relatively uniform distribution to one with an obvious peak. Additionally, the zenith luminance is up to 0.01cd/m(2), more than 50 times the standard dark sky luminance. Dalian experiences serious light pollution.