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New Lighting Law Protects Observatories

Photograph of the island of Hawai'i taken from the International Space Station by astronaut and former IfA solar physicist Ed Lu shows the principal sources of light pollution on the Big Island. The Hilo and Kona airports and Hilo harbor are among the brightest sources of light. Lava flows from the ongoing eruption of Kilauea are also visible.

Dark sky advocates in Hawaii recently scored a victory. The governor has signed into law a bill that requires the state Department of Transportation to comply with county outdoor lighting ordinances that are more stringent than state regulations when installing new outdoor lighting at airports and harbors, and along highways. The purpose of the law is to preserve the dark skies over Haleakala and Mauna Kea Observatories.

The bill, H.B. 155, noted that "one of the most critical needs for preserving the value of these sites is to reduce bright sources of light that penetrate the dark night sky. Recent nighttime images from the international space station revealed that some of the brightest sources of light on Maui and Hawaii are the airports and harbors on both islands. Astronomers on Mauna Kea are now detecting artificial light sources from urban areas that are diminishing the telescopes' ability to do research."

Hawaii and Maui counties have lighting ordinances that apply to outdoor lighting. On the island of Hawaii, outdoor lighting must be shielded; most outdoor lighting must use low-pressure sodium (LPS) lamps, which are nearly monochromatic (emitting light of a single yellow-orange color). Astronomers are better able to filter out light from LPS lamps than from broad-spectrum sources. Low-pressure sodium lamps are also the most energy-efficient light source available.

The Maui county lighting ordinance, which became effective in January 2007, requires most light sources to be fully shielded. Fully shielded lights direct light downward only, emitting no light directly upward. The Maui ordinance will require replacement of noncompliant lights within 10 years.

Maui Representative Joe Souki introduced the bill. The new law went into effect on July 1.