Flagstaff requires outdoor lights to be shielded from projecting into the sky. 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. Buffalo Park in Flagstaff, just a few miles from downtown, is about a 4 on the Bortle scale, which quantifies levels of light pollution. (The scale is from 1, which is the darkest possible sky, to 9, which resembles the light-polluted night sky of, say, New York City. To see the Milky Way, the sky needs to be less than 5.)
