What type of lighting emits the least amount of light pollution?
Peter Blado, Tacoma, Washington
October 1998 This nighttime satellite image shows where light pollution exists in the eastern United States and Canada. International Dark-Sky Association [View Larger Image] Second, use the correct amount of light. Overkill does not help visibility and it can waste a lot of energy. Going from darker areas to overlit areas means the eye does not adapt to the bright areas, and visibility is compromised. Follow the published guidelines of the Illuminating Engineering Society of North America. If you have chosen a good light fixture and used the appropriate amount of light, the choice of the light source is less important. In the vicinity of major observatories, and for those who want the maximum energy savings, one should use low pressure sodium (LPS) lights. These lights are essentially monochromatic, so astronomers can filter their emission out, and the sky remains dark at all other wavelengths. LPS is also the most energy-efficient light source. Many astronomers, however, prefer to use high pressure sodium (a sort of amber light) or metal halide (whitish) sources. HPS is fairly energy efficient, and metal halide is the most energy efficient of the white light sources. Dark skies need our help. Those with additional interest can go to the International Dark-Sky Association (IDA) website (http://www.darksky.org), which has links to other sites, including many in the lighting industry. Or write IDA at:
— DAVE CRAWFORD, IDA EXECUTIVE DIRECTOR |
