Darker Skies Over New Mexico

The night sky over New Mexico should soon be darker. Governor Gary E. Johnson signed the Night Sky Protection Act into law on April 6, 1999. The purpose of the law is “to regulate outdoor night lighting fixtures to preserve and enhance the state’s dark sky while promoting safety, conserving energy, and preserving the environment for astronomy.” Although Connecticut, Maine, and Arizona also have statewide restrictions on outdoor lighting, New Mexico’s new law is the most comprehensive.

Under the Night Sky Protection Act, all outdoor lighting fixtures over 150 watts that are installed after January 1, 2000 must either be shielded, which means that they cannot cast any light above the horizontal plane, or they must be extinguished between the hours of 11 p.m. and sunrise. Also, no new mercury-vapor outdoor lighting fixtures can be sold or installed after January 1, 1999. Mercury-vapor lights are a major contributor to light pollution, and are an anathema to astronomers because they emit light at wavelengths critical to astronomical observation (see