Blinding the Big Eyes

Environmental pollution is really a problem for everyone. It now turns out that even the nation's astronomers are bothered. With urban sprawl rapidly closing in on their lonely mountain observatories, the astronomers are faced with a problem of first magnitude: the glare of city lights is threatening to put some of the country's largest optical telescopes out of business.

California, in particular, is now becoming an astronomical disaster area. The blinding glow from nearby Los Angeles, for example, has rendered Mount Wilson Observatory's 100-in. telescope useless for the kind of observations of distant galaxies that once made it world-renowned. Not far behind is the 120-in. Lick Observatory reflector atop Mount Hamilton, which is rapidly being swamped by the incandescence of the San Francisco Bay Area's expanding cities and towns. Even the 200-in. Hale mirror on Mount Palomar--the world's largest telescope--may be seriously imperiled before the decade's end by the increasing glare of San Diego and Los Angeles.

Sensitive to Glare. With a million times the light-gathering power of the unaided eye, the giant telescopes are extremely sensitive to the slightest glare in the sky. Even the light from a city 50 miles away can blot out the dim specks produced on a photographic plate by a distant galaxy or quasar. Smog adds to the astronomer's headache; by scattering ground light in all directions, tiny smog particles can greatly increase the glare over an observatory. Not only the amount, but also the character of the light can affect a telescope's usefulness. Increasingly, mercury-vapor street lamps are the astronomer's special bane. They happen to be a powerful source of ultraviolet radiation, which is in the part of the light spectrum that gives astronomers important clues to the nature of certain stars and galaxies. And if a city's street lamps and billboards give off light characteristic of a star, explains Astronomer Halton Arp, hours of patient photographic work can be ruined.

Light pollution is a slightly less serious problem around the country's other major astronomy center, Tucson, Ariz., but astronomers there are already worrying about the glowing threat. The area's five major observatories--including Kitt Peak, which expects to unveil a 150-in. telescope next year--recently petitioned the town fathers to shield and filter all mercury-vapor street lamps, ban all but essential searchlights, and pave roads with blacktop instead of lighter, reflective concrete. Aware of the observatories' contributions to the local economy, the Tucson councilmen agreed to consider the requests.

Technological Tricks. In California, where brightly lit freeways and shopping centers are a way of life, astronomers have long since given up efforts to reduce the creeping glare. Says Horace Babcock, director of the Mount Wilson and Palomar observatories: "It's just not realistic for us to go out now and try to get the cooperation of 80 or so cities in shielding street lights and cutting glare." Instead, California astronomers are trying other tactics. With the help of computers, for example, they can work over stellar images and remove the worst effects of extraneous light during certain types of observations. But such technological tricks are only stopgaps. Most California astronomers agree that the day is not far off when they will have to transfer their telescopes to new peaks, if any suitable ones can still be found--or give up some of their most promising explorations of the universe.

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