Mt. Wilson Scans The Skies Again

INSIDE the great cathedral dome of the 100-inch Hooker telescope here sits a cane chair illuminated by a floodlight.

It is the place where Edwin Hubble, dressed in heavy tweeds of the day, sat many nights in the 1920s and 1930s as he made 20th-century astronomy's greatest discovery: the existence of an expanding universe.

Since the mid-1980s, the 100-ton instrument, eclipsed by other telescopes and inhibited by light pollution from nearby Los Angeles, has been in mothballs - a mountain-top memorial to epiphanies of astronomy past.

Now this once-great instrument made of French wine-bottle glass is about to be turned on again. The Hooker's "second light," expected to begin next month, is part of a quiet rebirth of what was once the world's premier astronomical facility.

Aided by new technology and an expanded research program, Mt. Wilson Observatory appears poised to play a significant role in science again.

Telescopes on this crown of pine and black oak in the San Gabriel Mountains are expanding their study of the enigmas of the sun and galaxy, helping in the search for intelligent life in the universe, and will soon beam planetary images into school classrooms.

Perhaps most important, the site has become a prime proving ground for an emerging technology that promises to revolutionize ground-based astronomy.

Sitting at a picnic table overlooking Los Angeles sprawling like a milky nebula below, Robert Jastrow, director of the institute that manages the observatory, says: "I think with all the things going for it, Mt. Wilson will regain its place among the leading observatories of the world."

From this picnic-table perch, it is easy to see why Mt. Wilson has harbored both potential and problems as a star-gazing site. On this day, as on most, a pot lid of smog extends over the city below. The air is trapped by an inversion layer, which is bad for earthlings but good for those looking heavenward. The inversion layer suppresses turbulence over the mountaintop, making 5,800-foot Mt. Wilson probably the best viewing peak in North America.

It was this stability of air that prompted George Ellery Hale and other early astronomers to haul, first by mule train and later by wheezing truck, a 60-inch telescope to the site in 1908 followed by the mountain's signature instrument, the 100-inch, in 1917. Growing urban glare

Over time, Los Angeles began to grow out below into something more than a thousand points of light. The glare hampered the ability of researchers to view faint objects deep in space, the prime focus of modern astronomy.

While the observatory remained an important place to study the sun and brighter stars and objects within our own galaxy, much of the interest - and money - in the field has gone into probing galaxies and objects at immense distances from Earth.

Thus most of today's big new telescopes peer up from remote locations, notably the Mauna Kea volcano in Hawaii and mountains in northern Chile. Indeed, Mt. Wilson probably reached its nadir in 1984 when the Carnegie Institution, its owner and prime patron since early this century, decided to shift financial support to telescopes in Chile, where the darker skies are better suited for cosmological research.

In subsequent years, the Mt. Wilson Institute, a group of volunteers, has been plotting the revival of the famed facility. The number of research projects at telescopes on the mountain has doubled in the past two years. The capstone of the observatory's reemergence will be the reopening of the 100-inch Hooker, named after a businessman who put up the initial money.

Using $100,000 donated by a local foundation, the institute expects to take its first images with the instrument in June. Another $100,000 is being sought to complete the renovation, which members hope will happen by fall.

When fully functioning, the 100-inch (the diameter of its light-focusing mirror) will still be a formidable scientific tool, among the dozen or so largest telescopes in the world.

"It is one of the star-class instruments, at one of the best sites in the world," Dr. Jastrow says.

From the inside, the telescope is a monument to girth and the ghosts of astronomy's past. It is held together by bolts and bearings and girders that befit a battleship. The dome is seven stories high and half a block across. It cinches open with a primordial groan.

Downstairs, the wood lockers where the Hales and Hubbles and others who made Mt. Wilson, in the words of Jastrow, "arguably the most important site in the history of astronomy," still stand, their names affixed to the doors with tape.

Standing out in a fraternity like this can be difficult: Albert Michelson, who first measured the speed of light by bouncing a beam off a nearby mountain, only merits an outdoor plaque and a toolshed named after him.

The biggest leap forward for Mt. Wilson in the future may lie in a technology called adaptive optics. It is designed to offset the effects of atmospheric distortion, a bane of astronomers since Galileo. Light rays from stars bend like straws when passing through Earth's atmosphere. This "twinkling" delights romantics but irks astronomers, yielding gauzy images.

The trick is to pass the jumbled rays through a "rubber mirror" - a deformable surface that can be flexed thousands of times a second - to straighten out the beams and produce a tightly focused spot.

Using adaptive optics on the 60-inch, astronomers at Mt. Wilson have produced the sharpest focus of any telescope of its size in the world. Applying the technology to the 100-inch, something Jastrow says will probably take another year and $250,000, would boost the instrument's ability to view our own and nearby galaxies - and offset some of the effects of light pollution.

"We will have the highest-resolution telescope that has ever existed on the face of the earth or in space," says Dr. Sallie Baliunas, an astronomer at the Harvard-Smithsonian Center for Astrophysics and deputy director of the Mt. Wilson Institute. Increased resolution

This isn't just home-mountain boosterism. Others working with the technology say that, when perfected and applied to an instrument the size of the Hooker, it should dramatically increase its resolution and reach. While Mt. Wilson will still never do deep-space research, it will broaden its role in studying the sun, nearby bright stars, and in the search for planetary systems.

"They will have the chance of taking some of the best images in the world," says Dr. Sydney Wolff, director of the National Optical Astronomy Observatories in Tucson, Ariz.

Other telescopes on the mountain are helping to search for extraterrestrial intelligence. A robotic telescope is being built that astronomers will be able to operate remotely.

Renovation of another reflector, a 24-inch, will bring the heavens into classrooms. Students will be able to call up the telescope's pictures, as well as other stellar and planetary information from a data bank, at the tap of a computer key.

Back at the picnic table, over an egg-salad sandwich, Jastrow reflects on these changes like a proud father. All this, he concludes, should restore Mt. Wilson's place in the pantheon as "America's Observatory."