For an astronaut looking out of the International Space Station windows, city lights are brighter than the stars. To tackle light pollution citizen scientists are urged to help map out the problem on their smartphones by identifying images of cities taken from space. Astronaut pictures are the highest-resolution, colour images of night available from orbit. "The International Space Station is the best observation point humankind has for monitoring Earth at night," says Kevin Gaston, project leader of the Lost at Night project that raises awareness of light pollution. There are half a million high-resolution pictures of Earth at night in NASA's Astronaut Photography of Earth archives.