Archive for Sunday, July 15, 2001

Astronomers try to take back night

July 15, 2001


— The stars at night don't appear as big and bright as they used to, thanks to cities washing out the sky with excessive, misdirected light, astronomers say.

The glow troubles astronomers trying to pick out faint nebulae, gaseous clouds and other distant phenomena. A group of Canadian astronomers has issued a "reward" for a missing galaxy: our own Milky Way.

The International Dark-Sky Assn., a group of about 7,000 astronomers, light engineers and other concerned people, is trying to reverse the brightening trend.

According to the association, light-pollution control laws have been enacted recently in six states: Arizona, Colorado, Connecticut, Maine, New Mexico and Texas. New Mexico bans so-called light trespass by homeowners whose outdoor lights spill onto neighbors' property.

The latest flashpoint is San Diego, where astronomers at Palomar Observatory home to one of the world's largest telescopes are trying to fend off a City Council proposal to use brighter streetlights.

Such "white" light can't be filtered out by the telescopes and would hurt Palomar's ability to see quasars and other objects in remote corners of the universe.

"It's a major threat," said Robert Brucato, assistant director of the observatory. "There are precious few telescopes left in the world to do the kind of research we do. We shouldn't throw these telescopes away with impunity."

In 1984, officials at Palomar, about 70 miles from San Diego, helped persuade council members to adopt low-pressure sodium streetlamps, which produce yellow light that stargazers can filter out as they focus on the feeble twinkle of stars millions of light years away.

"It is pleasing to the senses and intellect of man to be able to gaze at the night sky and see the planets, comets, stars and galaxies with a minimum of interference from light pollution," the council said in passing a light pollution ordinance.

But there is a backlash against the wan yellow light. The council will decide on Aug. 6 whether to convert 25,000 yellow streetlights to the brighter pinkish-white light of high-pressure sodium bulbs.

City officials say yellow lights make people feel unsafe and have made it hard for police to identify those lurking in the shadows, although they concede they have only anecdotal evidence to support that claim.

Mayor Dick Murphy has called the yellow light "a criminal's best friend." He said he also supports the change for aesthetic reasons: "People think they're ugly."

Astronomers also are concerned about a plan before the council to replace some hooded streetlights with decorative acorn-shaped lamps in various historic districts. The acorn lamps allow most of their light to shine upward, to the sky.

"They are blantantly inefficient," said Paul B. Etzel, director of the nearby Mount Laguna Observatory. "It's a 19th century solution to a 21st century problem."

Critics also point to higher costs. Getting rid of the low-sodium lights would cost nearly $2.8 million and raise the city's power bill by a half-million dollars a year, according to a city report.

"All of this when we're concerned about our energy and our costs seems to be really ill-timed," said Jay Reynoldson of International Commission on Illumination, an international body of lighting engineers.

Astronomers in Southern California, which has some of the nation's best atmospheric conditions for viewing stars, say they steadily are losing the night to light pollution.

Palomar Mountain was a remote outpost with clear, dark skies in 1934 when the California Institute of Technology chose a 5,600-foot-high spot there to build a 200-inch telescope that was then the world's largest. But rapid urbanization in Southern California and San Diego County has contributed to city "sky glow."

"The sky is about twice as bright as it should be," Brucato said. "If you double the amount of light pollution, you have to double the observing time to get the same results."

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