Sky brightness over the northeastern US. The major urban areas are evident, as are the relatively few dark sky regions in the US (far north in Canada there are large areas). The white dots indicate areas that are most favorable for astronomical observation – based on minimal light pollution. The northernmost is in upstate Maine, the next south is over the Aderondick Mountains, the third area is in Pensylvannia and the southernmost is on the Virginia – West Virginia border. There are other areas in the southeast US (not shown). Most of the NE US population is within a half-day’s drive on one of these regions.