Sky Quality Meter

The Sky Quality Meter (SQM) is an instrument used to measure the luminance of the night sky. It is used, typically by amateur astronomers, to quantify the sky glow aspect of light pollution, and uses units of "magnitudes per square arcsecond" favored by astronomers. SQM measurements can be submitted to a database on the manufacturer's website and to the GLOBE at Night citizen science project.

There are several models of SQM made, offering different fields of view (i.e. measuring different angular areas on the sky), and various automatic measurement and data logging or data communication capabilities.

The SQM is produced by the Canadian company Unihedron in Grimsby, Ontario.