Dark-sky Movement - Sky Glow

Sky Glow

Sky glow is the illumination of the night sky or parts of it resembling an orange "smog". It occurs from both natural and human made sources. Artificial sky glow is caused by the over-illumination of the sky from large city centres, shopping centres or stadiums. It consists of light that is either emitted directly upward or reflected from the ground that is then scattered by dust and gas molecules in the atmosphere, producing a luminous background or light dome. These artificial sky glows cause the sky to be 5-10 times brighter in urban areas than a natural dark sky that is unaffected by artificial light. Natural sky glow can come from natural lighting resources such as the moon, the stars, the sun or auroras.

Sky glow affects the ability to view stars which can be troublesome for astronomers who rely on the night sky for their research. Astronomers usually prefer very dry, very dark nights for observation.

Some communities are becoming aware of this problem and are putting forth efforts to minimize the hazy orange sky glow. A community in particular is the city of Merritt, British Columbia. In an article published July 8, 2010, it states that they are making minor changes to lighting in and around Merritt such as the installment of down cast lighting to commercial buildings as part of their light pollution abatement program. The benefits of this technological change include; "saving energy through better focused lights, preserving the environment by reducing excess light that may effect flora and fauna, reducing crime and increasing safety by more adequately illuminating areas, and reducing health risks."