Guide to measuring light pollution

Due to light pollution, the night sky over many cities is hundreds of times brighter than a natural, starlit sky. This artificial sky glow obscures the stars and disrupts the natural nighttime environment for people, wildlife, and ecosystems—even hundreds of miles from urban areas.

Understanding and solving light pollution requires reliable data, and one of the best ways to collect that data is by measuring the brightness of the night sky. Fortunately, there are many ways to contribute, whether you’re a citizen scientist, researcher, or simply curious about the quality of your local night sky.

Become a community scientist

Participating in community science projects is one of the easiest and most impactful ways to learn about and contribute to light pollution research.

Globe at Night

The Globe at Night campaign allows anyone to measure and report night sky brightness observations using a smartphone, tablet, or computer. No specialized equipment is required, although observations can also be submitted using handheld sky quality meters (SQMs).

Smartphone applications

Several smartphone applications make it possible to measure or estimate night sky brightness:

• Dark Sky Meter uses the camera sensor on compatible iPhones to estimate night sky brightness.
• Loss of the Night guides users through visual observations using the human eye to measure sky quality.
• MySkyatNight allows users to explore and analyze available night sky brightness data.
• Cities at Night engages community scientists in mapping nighttime imagery from the International Space Station to help researchers better understand light pollution worldwide.

Long-term monitoring and data standards

In addition to community science efforts, researchers and volunteers around the world operate long-term monitoring stations using permanently installed sky quality meters, including devices such as SQM-LU, SQM-LU-DL, and the SQM-LE. These instruments provide valuable data on how night sky brightness changes over time.

As the number of monitoring stations has increased, the scientific community has worked to develop common standards for recording and sharing observations. Standardized data collection methods make it possible to compare measurements across different locations, instruments, and time periods, helping researchers better understand global trends in light pollution.

Resources for sky quality meter users

For those interested in collecting and managing sky quality meter data, several tools and resources are available:

• PySQM — Software for collecting and processing standardized night sky brightness measurements.
• PySQM documentation — Guidance for implementing standardized sky glow data formats.
• Knightware SQM Reader — Software tools compatible with Unihedron sky quality meters.