Trespass Issues

Sky Glow


What is sky glow or light pollution?

Sky glow or light pollution is a condition where the night sky is illuminated when upwardly directed light reflects off particles in the atmosphere, such as moisture, dust, or smog. 

What does sky glow or light pollution do?

Sky glow produces a luminous haze and limits our ability to see the stars. Astronomers are concerned with sky glow, as they must filter it from their observations. The growth in popularity of amateur astronomy is producing an increased awareness of sky glow. A few states have declared the night sky to be a natural resource to be protected.

What is being done about sky glow / light pollution today?

Some efforts to reduce sky glow are rather straightforward use shields and visors on floodlights to limit uplight. Other attempts are not as simple as they seem. For example, eliminating high angle light (above horizontal) from streetlighting fixtures so that they cast all light downward will dictate that fixtures are placed closer together, increasing light reflected from the ground sky glow may actually intensify. When lighting is installed near a major astronomical observatory or an intrinsically dark area (national park), sky glow must be limited to low levels. In these instances refer to recommendations by the International Dark Sky Association (, an organization, founded by astronomers, who address this issue. For areas where observatories are not a concern, addressing the two other objectionable issues, glare and spill light, often will reduce sky glow to acceptable levels.