Night Sky Brightness Measurement, Quality Assessment and Monitoring

TL;DR

This paper reviews how natural and artificial factors influence night sky brightness, discusses measurement methods, and explores long-term monitoring techniques to assess sky quality for astronomy.

Contribution

It provides a comprehensive update on natural and artificial influences on night sky brightness and evaluates measurement and monitoring methods since the last major review.

Findings

Natural and artificial sources significantly affect night sky brightness.

Various measurement techniques are used to assess sky brightness.

Long-term monitoring is essential for understanding trends in sky quality.

Abstract

Ground-based optical astronomy necessarily involves sensing the light of astronomical objects along with the contributions of many natural sources ranging from the Earth's atmosphere to cosmological light. In addition, astronomers have long contended with artificial light pollution that further adds to the 'background' against which astronomical objects are seen. Understanding the brightness of the night sky is therefore fundamental to astronomy. The last comprehensive review of this subject was nearly a half-century ago, and we have learned much about both the natural and artificial night sky since. This Review considers which influences determine the total optical brightness of the night sky; the means by which that brightness is measured; and how night sky quality is assessed and monitored in the long term.