"The app lets citizen scientists like you measure how bright the night sky is, by seeing which stars you are able to see. The more faint stars you can see, the more natural your sky is. Your results are then shared with the GLOBE at Night project, and will be used to track how the night sky is changing in response to widespread adoption of LED lights."
In winter time, when nights become longer and darker, stargazing can be a fantastic experience and family activity. But in urban areas, the stars disappear behind the skyglow caused by waste light that shines up into the sky. This light pollution is not only a problem for astronomy. Scientists from the interdisciplinary project "Loss of the Night" study how it affects health, society, and the environment. In order to measure how skyglow is changing, they have developed an app for smartphones, which allows citizen scientists to count the number of visible stars in the night sky. The app, originally only available for Android, has now been expanded to support Apple's iOS."