Stargazers Cherish San Diego’s Orange Glow

The cry came from Palomar Observatory at the start of the decade: Turn down your lights!

And by now they mostly have.

The treasured astronomical finds being made from the world’s most famous observatory were being jeopardized by Southern California’s urban sprawl and the increasingly bright sea of street lights, illuminated billboards, parking lot lights and even front-yard landscaping lights pointing skyward. The problem didn’t exist atop Palomar when the observatory was under construction in the 1940s.

The primary culprits were mercury vapor or incandescent lamps that were washing the sky with unwanted white light. Astronomers atop Palomar Mountain found that their light-gathering telescopes, trained on ultra-faint stars, galaxies and quasars in the far corners of the universe, were being poisoned by man’s urban lighting.

So in 1981, the astronomers at the California Institute of Technology, which owns and operates the Palomar Observatory, mounted an intense public relations and political campaign to darken Southern California’s night sky.

They wanted outdoor light fixtures to be pointed downward. They asked that non-essential outdoor signs and billboards not be illuminated after midnight. And, most important, they wanted the state Department of Transportation, San Diego County and its various cities to convert their street and highway lights from the traditional white light to sodium light that--while unpopular in some corners because of its yellow hue--is less offensive to the telescopes atop Palomar.

The filters at the observatory can screen out the yellow light, while the low-pressure sodium bulbs effectively illuminate the same area.

One by one, the various public bureaucracies, sympathetic to the nature of astronomical research and not wanting to render useless one of Southern California’s greatest scientific tools, cooperatively fell in line to reduce the light pollution.

Generally, they agreed that when the old lights burned out, they would be replaced with the sodium fixtures. New housing and commercial developments were required to install the yellow lights from the beginning.

“We’ve had excellent cooperation and results,” said Robert Brucato, the observatory’s assistant director. “If the controls hadn’t been put in place by the various agencies, we’d be in very bad shape right now.”

Bob Thicksten, the observatory’s superintendent, admits the new-generation public lighting casts an eerie glow over San Diego County.

“Sometimes I’ll get up in the middle of the night to check on things and I’ll do a double-take when I look to San Diego,” he said. “The region is in an orange-ish glow, like a distant forest fire.”