Lighting Our Skies
Over the past decade, the International Dark Sky Association (IDA) has become a significant participant in the field of residential and commercial lighting design. Originally founded in 1988 by a group of concerned astronomers, the IDA was created in response to the growing amount of lighting pollution in and around major metropolitan areas. This lighting pollution, which brightens the overhead sky, is called sky glow.
The increase in urban sky glow has adverse effects on our ability to view the night sky. It is believed that about two-thirds of Americans can no longer discern our own galaxy, the Milky Way, with the naked eye. About 2,500 individual stars should be visible to the human eye in an unpolluted night sky. However, in a typical suburb only 200 to 300 stars are visible, and in the city fewer than a dozen stars may shine through the ever-present sky glow.
“The increase in urban sky glow has adverse effects on our ability to view the night sky.”
The goal of the IDA was and is the improvement of the night time environment through intelligent, energy efficient exterior lighting design. Through its lifespan, the International Dark Sky Association has worked with local governments to encourage the adoption of lighting ordinances that are ‘dark sky friendly.’ Through these ordinances, the IDA hopes to curb sky glow and to reduce electricity waywardly spent in lighting the night sky. For instance, the IDA estimates that as much as 30 percent of light produced in traditional decorative ‘acorn’ style fixtures is wasted on lighting the sky above. The wasted light only serves to increase sky glow and drain our electrical energy stores.
For both lighting ordinances and lighting design, the IDA recommends, as a minimum:
- Using ‘full-cutoff’ fixtures for parking lot and other large area lighting. A full-cutoff fixture does not emit light above the horizontal plane of the fixture.
- Establishing guidelines to prevent over-lighting and wasted energy.
- Limiting the amount of “light trespass,” lighting that crosses from one property to another.
- Creation of exterior lighting control scenarios to turn off unnecessary lights when they are not needed.
- Using only energy efficient lamp sources.
- Using top-down lighting for outdoor signs.
Slowly but surely, lighting ordinances around the country are changing, affecting the way exterior lighting is designed, manufactured, and installed. The new ordinances can be challenging to meet; however, the result is improved nighttime lighting designs that are visibly pleasing, protective of the night sky, and energy efficient, all while maintaining safe and maneuverable walking and driving environments.
Today, the IDA boasts over 10,000 members representing a large cross section of society including community residents, government officials, industry manufacturers, design professionals, and astronomers. For more information on the International Dark Sky Association and their work in your area, visit their web site at www.darksky.org.
– Eric S. Nielsen, PE