Flagstaff mandates that outdoor lighting be shielded so it doesn’t point skyward. There are also limits on the lumens of light allowed per acre of land.
The result is a starry sky that can be seen even from the heart of the city. Flagstaff Buffalo Park, located just a few miles from downtown, measures about 4 on the Bortle scale, which measures the level of light pollution. (The scale runs from 1, the darkest possible sky, to 9, similar to the light-polluted night sky in New York City, for example. To see the Milky Way, the sky must be less than 5.)