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NSAW aims to reduce light pollution for U.S. Naval Observatory operations

Personnel at the U.S. Naval Observatory in Washington, D.C., prepare the facility's historic 26-inch refractor telescope for optical viewing of Mars. NSAW is working with the communities around the observatory to limit light pollution that makes it difficult for astronomers to view the night sky. (U.S. Navy photo by Chief Warrant Officer 4 Seth Rossman)

06/18/15 12:00 AM

By Patrick Gordon
NSAW Public Affairs Office

The U.S. Naval Observatory is a very famous place. Most know it as the residence of the vice president of the United States. But what many people don’t know is that it is a fully functioning observatory, determining the motions of celestial bodies and providing astronomical and timing data required by the Navy and other components of the Department of Defense for navigation, precise positioning, and command, control, and communications.

But this necessary and precise research is being hindered every night by light pollution, and the culprits often have no idea they are doing it.

“Since the Naval Observatory still has working telescopes, in particular the 26-inch telescope, light pollution makes it difficult for the scientists to see the stars, and urban light pollution in the D.C. area is a problem,” Janell Herring, community planning liaison officer for Naval Support Activity Washington. “What we’re trying to do is make the public aware, so we can turn down the lights and prevent or turn back the current level of light pollution and the encroachment to the Navy’s mission.”

According to the observatory, light pollution can be categorized into two forms - sky glow and light trespass. Sky glow is a generalized effect resulting from the scattering of light from sources throughout a city or metropolitan area. Light trespass refers to the escape of light from direct point sources.

Herring explained that because of the observatory’s location in an urban area, the amount of light being thrown into the air at night creates conditions that make it difficult for astronomers at the observatory to use their instruments to watch the night sky. In an effort to reduce this, Herring said that NSAW has worked with a number of community organizations to raise awareness about what citizens can do to help.

“We do a lot of outreach and have brought in groups in D.C.’s government, such as the D.C. Office of Planning, Office of Zoning, Office of the Environment, and the D.C. Department of Transportation,” said Herring. “And then we go out to the neighborhood associations and the National Capital Planning Commission and do briefs for them, so that when they make decisions on projects they take our concerns under consideration. And there are things like Glover Park Day. Glover Park is a neighborhood just outside of the observatory and every year they have Glover Park Day, so we go out there and raise awareness among the residents out there.”

Herring added that her office has worked with the D.C. office of zoning and have incorporated some of the best management practices for light pollution into D.C.’s zoning code, working with developers to stop the problem of light pollution at the onset.

She explained that are a number of things that average citizens can do as well to limit the amount of sky glow around the observatory.

“Three things that people can do are only have the lights on when you need them, only have lights where you need them, and turn down the wattage,” said Herring.

Some tips for limiting light pollution are:

· Keep lights off when not in use. Hooking up motion sensor to lights is a good way to ensure that they are not on when they don’t need to be.

· Use lower wattage bulbs. Lower wattage bulbs reduce the amount of light being cast out. Herring said that foot-candle tests by the Dark Sky Association and the Illumination Engineering Society found that wattage in neighborhoods around the observatory were well above recommended levels. “We’re just over lighting in most cases,” said Herring.

· Know the Glow. The type of bulb affects the color of light it puts out, said Herring. She recommends using low pressure sodium lights wherever possible because they put off a yellow light that can be filtered by the telescope. Commonly used bulbs, such as LED bulbs, produce broad spectrum light, which is much more difficult to filter.

· Point lights down when possible. “Light pointed at the ground tends to stay on the ground,” said Herring. Lighting fixtures should direct light where it is needed rather than scattering it. Full cutoff fixtures shine light downward rather than allowing it to escape in all directions and contribute to sky glow.

Herring said that while more work needs to be done to reduce light pollution in the area around the observatory, outreach has proved dividends. She added that many members of the surrounding neighborhoods have become more aware of the Naval Observatory’s mission and how they can help due in large part to interaction with the community.

“We’ve seen a lot of awareness of the issue,” said Herring. “The difference between going out to Glover Park Day the first year and the following year was noticeable. The first year nobody knew there was a working telescope at the observatory, but the following year a lot of people came up to us and told us they were aware of the telescope and the problem.”