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Palomar's telescope mirrors maximize seeing

The Hale blinks

The Hale is currently the largest working telescope in the world, but that claim to fame will not hold for much longer.
  • The Hale is currently the largest working telescope in the world, but that claim to fame will not hold for much longer.
  • Image by Robert Burroughs

Twilight has ebbed to a fringe of lapis on the western horizon, and the stars spin slowly as the dome of the 200-inch Hale telescope on Palomar Mountain blinks awake. Bob Thicksten, the observatory's superintendent, stands on the catwalk that rings the outside of the seven-story dome. We float through space, about 100 feet up, as the dome and the telescope turn toward a distant galaxy. The motion is so smooth and silent that it's easy to imagine that the dome is stationary and the sky itself is moving. The orange glow of San Diego and Los Angeles shimmers to the west and north, separated by the long, dark stretch of Camp Pendleton. To the northeast, behind the black hole of Mt. San Jacinto, the faint light of Palm Springs is just discernible. The silver-flecked, deep sable canopy of the sky envelops everything so totally that the white dome, only an arm’s length away, is nearly invisible. Thicksten is silent for a moment, taking it all in. He’s been here for 13 years, and the scene still mesmerizes him.

Palomar Observatory. We float through space, about 100 feet up, as the dome and the telescope turn toward a distant galaxy.

Palomar Observatory. We float through space, about 100 feet up, as the dome and the telescope turn toward a distant galaxy.

“I’d have been more of a doomsayer ten years ago,” Thicksten says, talking about the light pollution around Palomar Observatory. San Diego has adopted low-pressure sodium street lighting, and the 50,000 people due to move into the highway 79 corridor to the northeast in the next ten years will probably also be living under that same orange glow. Astronomers can filter out most of the sodium light, but there are plenty of skeptics who believe that in 20 years Palomar will go the way of its forebear, the 100-inch reflector on Mt. Wilson in Los Angeles. For the last five years, the Mt. Wilson telescope, which began operation in 1917, has been shut down because of light pollution. But Thicksten remains optimistic. “With all the new instrumentation, we’re holding our own.”

“I’d have been more of a doomsayer ten years ago,” Bob Thicksten says, talking about the light pollution around Palomar Observatory.

“I’d have been more of a doomsayer ten years ago,” Bob Thicksten says, talking about the light pollution around Palomar Observatory.

It’s cold out here, just the way astronomers like it. Through the blackness, Thicksten leads the way back inside, to the heated data room, one of several rooms that ring the dome that houses the main telescope. In the data room, three astronomers and the telescope operator, called the night assistant, are working. The astronomers are itinerants, passing through for three or four nights of work, while the caretakers like Thicksten and most of his 30 or so maintenance workers live on the observatory grounds. Thicksten uses a flashlight to illuminate a path to the data room, but this is just a courtesy, for my benefit. Like most Palomar staffers, he can navigate inside the observatory dome in total darkness.

Inside the dome. Like most Palomar staffers, Thicksten can navigate inside the observatory dome in total darkness.

Inside the dome. Like most Palomar staffers, Thicksten can navigate inside the observatory dome in total darkness.

The light in the cramped data room is blinding, at first. Thicksten introduces Juan Carrasco, the night assistant. Carrasco is 59, a former barber, meticulously groomed, outfitted in the plaid shirt and down vest that’s a virtual uniform for the observatory crew. His fresh-shaved face and warm demeanor belie the time of day; it’s morning for him. He’s in the middle of his usual ten-nights-on, four-nights-off schedule, six p.m. to six a.m., which he has kept for most of his 21 years here. Right now he doesn't have much time to talk, as the three astronomers in the room are busy trying to calibrate a 1500-pound spectrometer bolted beneath the 200-inch mirror of the Hale telescope. They are trying to line up the telescope with a guide star in order to check the instrument’s focus.

Russ Day's job entails everything from painting the 12 residential cottages to operating the 50-ton utility crane located in the top of the Hale’s dome.

Russ Day's job entails everything from painting the 12 residential cottages to operating the 50-ton utility crane located in the top of the Hale’s dome.

“Okay, Juan," remarks astrophysicist J.B. Oke (pronounced Oak), “we need to go 20 north.”

“Twenty north.” Carrasco repeats the command and taps a few keys on one of the computer terminals in front of him. A few steps away in the dome, gears in the guide system of the giant telescope move almost imperceptibly, nudging a million pounds of steel and glass 20 arc seconds across the sky. (Astronomers divide the 180-degrees of sky stretching directly overhead from horizon to horizon into 648,000 arc seconds.) Oke and two colleagues, John Hoessel of the University of Wisconsin and Marc Postman of the Space Telescope Science Institute in Baltimore, are staring at a high-resolution video monitor. On the screen are three images of the same star, forming a shape like a fuzzy donut.

A diagram of Earth

A diagram of Earth

“Thirty north, Juan.”

“Thirty north.” Classical music plays softly in the background. Oke, a noted Caltech scientist, is 62 and looks like Norman Rockwell’s idea of an astronomer. Lanky, silver and gray, wearing a comfortable old sweater, he suffers ignorant questions about his life’s work with the aplomb of a secure intellect. He sits with the two younger men (Hoessel is 39, Postman 32) in a narrow section of the data room, squeezed between a wall covered with bulletins and a bank of computer keyboards and video monitors. Juan Carrasco sits to Oke’s left, surrounded by computer terminals and digital readouts indicating wind speed and the temperature of the outside air, the dome air, and the 200-inch mirror.

Jeff Phinney (center) first became intrigued with Palomar after he spent time there in sixth-grade camp.

Jeff Phinney (center) first became intrigued with Palomar after he spent time there in sixth-grade camp.

Tonight the men are engaged in photometry, measuring the brightness of some of the most distant galaxies in the universe, using a spectrometer called the 4-shooter. The instrument detects light 200 times more efficiently than the photographic plates that were in use when George Ellery Hale started working on the 200-inch telescope in the 1920s. The 4-shooter’s light-gathering technology was developed for spy satellites and is now so refined that there is no further room for improvement in detecting the faintest glimmers of light in the farthest reaches of time. More recent advances allow astronomers to see many more objects at once but cannot collect any more light from them.

The Monastery - the lodge where the astronomers eat and sleep.

The Monastery - the lodge where the astronomers eat and sleep.

Oke reads off some star coordinates, and Carrasco slews the 60-foot-long telescope as fast as it will move across the sky. (The scope scans from horizon to horizon in two minutes.) A star field sweeps up onto the video screens. Most of the small dots are galaxies, filled with billions of stars. Marc Postman runs a computer program that measures how good the seeing is tonight.

He calls out, “One point six-five arc seconds," the diameter of a certain star that the telescope is producing on the screen. “This is not too good,” Carrasco explains, “but they’ll have to live with it.” If the seeing were excellent, say 1.4 or 1.2, the blurred images on the screen would be more like pinpoints.

Luz Lara in the middle of the mirror. Lara started working at Palomar for $1.25 an hour in the late 1950s, when he couldn’t speak a word of English.

Luz Lara in the middle of the mirror. Lara started working at Palomar for $1.25 an hour in the late 1950s, when he couldn’t speak a word of English.

On the bulletin board behind the astronomers is a page of “Calvin &i Hobbes” comic strips depicting Calvin as “Stupendous Man,” who steals the 200-inch “lens” at Palomar and uses it to direct sunlight to obliterate his elementary school. Astronomers have penciled in technical corrections to the cartoon copy in the margins between the strips. Nearby is a graph depicting the seeing trends at Palomar. Between 1987 and 1988, average seeing improved from 1.6 to 1.4 arc seconds reflecting similar improvements in seeing among telescopes worldwide.

As light-sensing instruments have advanced, telescope mirrors, which deliver the light to the instruments, have become the center of efforts to maximize seeing. Astronomers can’t do anything about the roiling winds in the upper atmosphere that cause distortions in the starlight before it reaches the mirror. But a problem they can work on is the distortion caused by heat near the telescope itself. Years ago, when astronomers actually worked in the same room with the telescope, their own body heat was enough to cause serious light distortion. Moving the observers out of the dome itself helped, but local heat sources still affected the seeing.

Two men and a woman rinse natural sea sponges in distilled water in preparation for cleaning the mirror.

Two men and a woman rinse natural sea sponges in distilled water in preparation for cleaning the mirror.

In 1985 the observatory’s overseers at the California Institute of Technology conducted an infrared survey around the dome to discover other heat sources. The resulting video showed electrical cables glowing through eight inches of concrete, long-forgotten transformers still radiating heat through the walls, and other similar problems. The observatory crew launched a large-scale attack on these heat sources, including the installation of an improved ventilation system, buttoning up the hot data room in slabs of insulation, and adding another layer of insulation beneath the floor of the telescope. The exterior of the dome, which had been a light beige, was painted a brilliant titanium white. But even with the continuing war on heat, Palomar will never be as heat-tight as newer telescopes, such as the 394-inch, $90 million W.M. Keck telescope in Hawaii. Its heated data room isn’t even in the same building as the telescope.

“Twenty-five north, Juan.”

“Twenty-five north.” Carrasco notes that the wind is coming out of the east tonight, bringing heat from the desert. Not good for seeing. “We do pretty good with a northwest wind or a west wind,” he says. After 21 years at Palomar, you learn a lot of the little things like that. Carrasco had worked at the McDonald Observatory in southwest Texas before coming to California, and he learned there that a telescope jockey needs to know his animal intimately. Astronomers can be a prickly bunch, having to wait months or years to get just a few nights on a telescope, so operators like Carrasco have to be able to move and point the instrument very quickly. “I’ve had eight astronomers in here, all arguing about what they wanted to look at,” he chuckles. But mostly, due to careful planning about how they want to work on any given night, astronomers know what they want to do, and when. This is one reason why Palomar, still the most productive telescope on the planet, remains a favorite of many astronomers. “It works every night and never breaks,” says John Hoessel.

One of the things that makes it work so well is its computerized guiding system, installed about 12 years ago. Before that, Carrasco used six small buttons to move the telescope in two directions — right ascension (east and west), and declination (north and south). Analog dials indicated the position of the telescope. The buttons and dials are still in place beside the computer terminals, like vestigial organs, drawing an occasional glance of longing from Carrasco. “The computers are much more accurate, and faster," he admits, "and I don’t have to think. But I’m not an artist anymore.”

Carrasco had to know the personality of the Hale telescope, how much the guiding motors in the 530-ton behemoth would coast after he took his finger off the button, and which way the telescope’s skeleton would flex, and by how much, when it was pointed in a certain direction. All of that flexure and play has been translated into computer programs, which automatically compensate for the little twists now. Oke, who ran Palomar for Caltech between 1970 and 1978, calls this advance in targeting the telescope "an order of magnitude better.” In 1977, the average telescope setting took 15 minutes; today the average is 2 minutes. Not that Carrasco, who had to do a mind-meld with the cold creature every night, wasn’t a wizard at aiming the Big Eye. “I had a feel for it,” Carrasco says, smiling wistfully. “We became artists. Now I just push buttons.” But he’s not complaining.

Russ Day pops into the observing room to say hello to Juan. Day, a strapping 37-year-old with a red beard, is typical of the Palomar crew in that his job entails everything from painting the 12 residential cottages to operating the 50-ton utility crane located in the top of the Hale’s dome. “When Juan trained me [as night assistant] ten years ago, it was a lot busier,” Day remarks. The night assistant would sometimes have to run out to the dome, which occasionally got stuck as it turned, and give an educated shove to a small control wheel so that the dome slit stayed lined up with the telescope. A clutch in the right ascension drive mechanism would slip occasionally, and the night assistant would have to hustle to fix it while astronomers sat watching the minutes tick by.

Sometimes the pumps that float the telescope’s main bearings on a thin film of oil would overheat, and the night assistant would have to cool the oil with dry ice. But these days, there’s a new clutch that never sticks, the oil pumps have been improved, and the dome slit stays lined up with the telescope by means of a 300-foot-long bar code pasted around the inside circumference of the dome.

Day agrees to conduct a short tour through the blacked-out spaces inside the dome itself. His faint flashlight beam sweeps across narrow catwalks, enclosed passageways and heavy, Depression-era equipment, as the Hale telescope swings and aims unseen in its dark lair. On the mezzanine level, about 15 feet below the telescope, a high-pitched whine grows louder as the flashlight approaches. The beam falls upon two small pumps, which provide the pressurized cushion of oil on which the telescope turns. One of several new engineering concepts that were developed by the telescope’s builders in the 1930s, this oil-film bearing allows the million pounds of the telescope to float almost frictionless on several sets of oil-impregnated pads. Four sets of these pads lie beneath the horseshoe bearing on the north axis, which is 46 feet across and remains the biggest bearing ever built. This and other technical innovations prompted one science magazine to declare the Hale telescope "a kind of overachievement for its time, an astronomical tour de force."

And yet, just a few paces around the dome on the mezzanine, is a paradoxical statement on the simplicity that underlies much of the telescope’s technical virtuosity. Day’s flashlight beam illuminates an electrical panel that’s straight out of a Frankenstein movie. A black bank of switches, gauges, moving electrical contacts that give off sparks, and one-of-a-kind gizmos stands in mockery of modem solid-state pretensions. By comparison, the next great advance in viewing the universe — the Hubble space telescope — is several orders of magnitude better. But the Hale works. The Hubble, for all its technical sophistication, doesn’t.

On my second night in the observing room, Hoessel, Oke, and Postman are once again huddled in front of video screens. But tonight, light winds are from the west, and the seeing starts out good, 1.3 arc seconds. This is a fourfold increase in the amount of light delivered to the spectrometer, compared to the night before. The scientists are running spectrograms on two clusters of galaxies. They ask Juan Carrasco to point the telescope at 21 hours, 43 minutes, and 44.1 seconds of right ascension; and 5 degrees, 16 minutes, and 30 seconds of declination. It’s pointing in the direction of the celestial equator, capturing the faint light of a cluster of galaxies the astronomers have tabbed 21FFS557. They’re looking at a point in time that’s about eight billion years old — almost halfway back to the beginning of the universe.

Conditions are perfect. The outside temperature is 13.8 C, temperature inside the dome is 11.7 C, and the mirror temperature is 11.2 C. “It’s warmer outside than inside,” observes Hoessel, standing behind his colleagues and rubbing his belly in a circular motion, a habit he’d probably be surprised to learn he had. “That’s just the way you want it.”

Hoessel has a lot of things going his way tonight. It’s his and Postman’s turn to control the music, and Hoessel pops Bob Marley’s greatest hits into the tape deck.

Last night the classical music seemed fitting, but now the timeless reggae rhythm blends surprisingly well into the jumble of computers and video star clusters.

  • It’s been three years since I’m
  • Knockin’ on your door
  • And I still can knock some more
  • Oooooh girl, oooooh girl
  • Is it feasible? I wanna know now
  • For I to knock some morel

The astronomers have been working on this same project for 17 years, and technically, it falls into the realm of cosmology — the study of the evolution of the universe, whose earliest advances were pioneered by Edwin P. Hubble. The scientists are trying to measure the distance to about 200 of the farthest galaxy clusters in the universe. They are also attempting to determine the speed at which the galaxies are moving away from each other. This information will be compared to the speed of younger galaxies closer to the Earth in an effort to demonstrate whether the older galaxies arc slowing down. If they are not, then scientists might hypothesize that the universe will continue to expand forever.

But if the distant galaxies are losing speed, perhaps the expanding universe will stop one day and begin contracting, to end eventually in a kind of Big Squeeze. When asked how many more years the project will take, the three of them look at each other and laugh.

“Okay, go about .5 south, Juan."

“Point five south." Carrasco commands just a slight rattle of a gear tooth on the telescope’s drive mechanism, like blowing lightly against a locomotive hanging on a string. He’s lining up eight galaxies into tiny slits cut into a piece of film mounted in the spectrometer. Once everything is set, the astronomers command the spectrometer to begin a 4000-second exposure, and they now have an hour and seven minutes on their hands.

Oke begins writing up a “pink sheet,” which denotes a problem on the telescope that needs to be fixed — an intermittent jerk or shimmy that’s obviously not related to the winds, which are nearly calm tonight. Marc Postman retrieves a wide-field picture of the area of deep space the telescope is pointing at. Dots of light are scattered in a blizzard across this patch of sky. “Each square degree here contains about 26,000 galaxies,” he says, “many of them brighter than our own.” Though each of these galaxies contains billions of stars, no single star is discernible by any method presently available to astronomers.

John Hoessel remarks that astronomers can only pick out stars in the 20 or 30 galaxies that are nearest to the Milky Way. "The Hubble [space telescope] was supposed to see individual stars in the Virgo cluster,” Hoessel says, his voice trailing away. On cue, Marley fills in the blanks.

  • Oh please/Don't you rock/My boat
  • ’Cause I don’t/Want my boat/To be rockin'...
  • I like it, like it like this ...

It’s impossible to avoid drawing comparisons between the Hubble space telescope and the Hale on Palomar Mountain. Some of the astronomers who spend time at Palomar have either had projects set back years because they were planning on using the Hubble — whose flaw wasn’t discovered until after it was placed in orbit 385 miles above the Earth — or have been asked informally for help in brainstorming solutions to Hubble’s problems. John Hoessel fits both of these categories.

Postman announces that the seeing has improved to 1.1 arc seconds, and Hoessel says, “Point six is about as good as you can get here. That’s the limit of the 200-inch minor. The Keck is supposed to go to .2 or .3. The space telescope was supposed to go to .05.” Hoessel speaks of the Hubble with a mixture of veiled anger, resignation, and determination, though still with his irrespressible good humor. He had been excited about the prospects of the Hubble’s seeing objects that were ten times fainter than could be discerned from ground-based telescopes. He was looking forward to examining the findings wrought by one of the Hubble’s special capabilities: making very bright stars fainter, so that smaller objects around the stars, such as planets, might be observable. “That capability is just lost now," he remarks.

Recently, space telescope managers have been discussing a fix-it scheme that would entail replacing Hubble’s high-speed photometer with an instrument containing several small mirrors. These mirrors would be specially shaped and pointed in a direction that would correct for the distortion in the main, 94-inch mirror aboard the telescope. But even these fixes, which would be accomplished by a space shuttle crew in 1993, would not bring the telescope back to its full capabilities. As Hoessel uses a whiteboard and an orange marker to draw schematics of the proposed fixes, Marley’s “Redemption Song” eases through the speakers.

  • But my hands was made strong
  • By the hand of the almighty
  • We forward in dis generation
  • Triumphantly ...

“I thought I was going to be doing science for the next few years,” Hoessel says, putting down the marker. “And now it looks like we’re going to be screwing around with equipment." Out of necessity, many astronomers are also engineers who develop and fine-tune their own sensing equipment. But in the Hubble project, all of that engineering work was supposed to have been included in the $1/2 billion purchase price. The Hubble’s flaws are expected to cost another $40 or $50 million to correct.

  • How long shall they kill our prophets
  • While we stand aside and look?
  • Some say it’s just a part of it
  • We've got to fulfill the Book

One could make harsh comparisons of the methods used to design and construct the Hale and the Hubble. Sixty years ago, the Hale’s designers made a decision to be receptive to any good idea, no matter where it came from. Although the design group was deliberately kept small, people literally off the streets who claimed to have a solution to a particular problem were welcomed in for a hearing. Fewer than 300 people were involved in designing and building one of the great scientific instruments of the century, and they did it when the country was in the midst of the Depression. It cost about $6 million, started working in 1949, and will probably continue working for at least another 30 years. It should be noted that the concept of contracting work to the lowest bidder was anathema to the builders of the Hale.

By contrast, at least 5000 people were involved in designing and building the $1.5 billion Hubble space telescope. But the construction of the mirror, the most crucial part of the instrument, was performed in a closed shop. According to the investigative panel that recently completed a report on the Hubble’s problems, only one quality control officer from NASA was on duty when the mirror was being made at the Perkin-Elmer Corporation in Danbury, Connecticut. Department of Defense directives severely hampered the ability to keep a close eye on the mirror fabrication process because the contractor was also involved in classified projects for the U.S. government. Many tests that could have detected the flaw in the mirror were not conducted because the mirror’s manufacturer was being pressured to finish the job. Although at least one set of tests did detect a flaw, the tests were rejected as unreliable. In this advanced era of technology, the weak link in the chain turned out to be people.

  • Won’t you help to sing
  • Dese songs of freedom
  • 'Cause all I ever had — ,
  • Redemption songs ...

Finally, a spectrogram sweeps onto the video screens, and the three astronomers pounce on it. As they ruminate over the meaning of certain faint lines, I remark that it appears that they do a certain amount of analysis on the spot with the raw data. “There are some discoveries made here,”

Oke acknowledges, “but most of the time it requires analysis later. We’re just trying to figure out why this line shoots across here.” He points to a barely discernible slash across the black-and-white bands of the spectrogram. Could it be a UFO? They chuckle at the question. Finally, I cannot resist asking if, given their universe-wide perspective, they think life exists on other planets. They’re sure of it.

“Probably millions of planets support life,” Oke declares. They find organic chemicals dispersed like confetti throughout the universe. In the farthest reaches of the void, they have detected molecules of water. Marc Postman says it’s not so much a question of whether life exists elsewhere; the question is, what’s the probability that civilizations will tend to destroy themselves once they develop technology? He says somebody has already worked out an equation to investigate that question.

Though the Hale has not yet discovered civilization anywhere in the universe, it has provided new information on the expansion of the universe and the evolution of galaxies, and it was a prime tool in the discovery of quasars, which are the most remote as well as the brightest objects in the universe. Quasars may be the cores of exploding galaxies.

Has Oke ever had a Eureka! discovery while sitting in the data room? He thinks for a moment, then blooms with the sudden recollection. “One year (Jesse) Greenstein and I were working on something we thought was a white dwarf. It was listed in all the white dwarf catalogues.

I got a spectrum on it and realized it was a quasar, not a white dwarf.” He looks at the other two astronomers, younger men who are enjoying the story as if it were a parable. “It was probably the biggest distance mistake that’s ever been made! It had been thought that the white dwarf was just a few parsecs away, but it turned out to be a quasar, two or three billion parsecs away!” They all laugh appreciatively, and I join them, even though for all I know a parsec is some kind of vegetable. Only later I learn it is a unit of measurement equal in distance to about 3.26 light years.

In 1928, George Hale, founder of the Mt. Wilson Observatory, was in search of grant money to build a telescope twice as big as Mt. Wilson’s 100-inch reflector. His search ended during a meeting with Dr. Wickliffe Rose, president of the Rockefeller General Education Board, in New York City. According to one account, when Rose informed Hale that the Rockefeller philanthropies would underwrite the entire $6 million cost of the project, Hale reacted by blurting out his favorite quote from Jules Verne: “A frightful cry was heard, and the unfortunate man disappeared into the telescope!"

The slightly altered quote is from Verne’s novel From the Earth to the Moon and a Trip around It, published in 1865. In Verne’s story, two men are in the focus cage near the top of a giant telescope when they receive news that their friends, who have been shot toward the moon by an immense artillery gun, are on their way back to Earth. One man tears open a telegram and utters a shout.

“What!" says the other observer.

"The projectile!"

“Well!"

“Has fallen to the earth!"

Another cry, this time a perfect howl, answered him.... The unfortunate man, imprudently leaning over the metal tube, had disappeared in the immense telescope.

After the man was fished out, unhurt, from the telescope’s innards, he exclaimed, “Ah! If I had broken the mirror?” “You would have paid for it,” replied his companion, severely.

To view the Hale telescope today is to see just how right, and how wrong, Jules Verne was. In the 1860s, before any truly large telescope existed, Verne envisioned one with a lens 16 feet in diameter, weighing 15 tons. An "ingenious mechanism" would allow Verne’s telescope to be pointed anywhere in the heavens and to follow the stars across the sky automatically. Though the Hale telescope is a reflector, not a refractor, and thus uses a mirror instead of a lens to focus starlight, its mirror is just over 16 feet across. It uses an ingenious mount to allow it unrestricted access to the sky. And yes, a person could fall into the telescope itself from the prime-focus cage, located high above the mirror. But if he broke the mirror, which is unlikely since it is made of extremely hard, two-foot-thick Pyrex, he surely could not pay for it. Hale’s 200-inch mirror is priceless and irreplaceable.

The mirror is mounted at the bottom end of a 60-foot-long skeleton of steel beams fused to a circular cage — the prime-focus cage — at the upper end. Unlike steel bridges or buildings, this tubular structure is not designed to flex and bend but must stay rigid. One of the telescope’s technical innovations was the system of angled beams, named the Semirier Truss (after its engineer, Mark Serrurier) that keeps the telescope’s primary mirror aligned with the secondary mirror at the other end of the tube. This concept became standard on other large telescopes. Hale’s telescope tube is cradled in a massive, 75-foot-long yoke that rotates east and west on the pressurized oil pads. For its size and mass, the whole arrangement looks oddly agile, kinetic, and somehow animate.

Viewed from the floor of the dome, the telescope can accurately be described as awe-inspiring. Something about its colossal size and elegance affected my breathing every time I looked up at it. The sweeping gray girders and trusses are as massive as those on a skyscraper, and yet the whole arrangement is so perfectly balanced and smoothly mounted that only a one-twelfth horsepower motor — the power required to run a sewing machine — is needed to turn it. The yoke that holds the telescope is fixed permanently at an angle that brings it exactly parallel to Earth’s polar axis, which is to say, the latitude of Palomar Observatory: 33 degrees, 21 minutes, 20 seconds. This allows the machine to move on just one axis while it tracks stars across the sky. Huddled within a soaring, brushed-aluminum cocoon, where every sound is artificially magnified and echoed, the telescope nonetheless seems to exist in a state of nature, like Stonehenge, its Bronze Age antecedent. There’s something frightening about it, as if it can know things that are beyond human comprehension. People tend to speak in hushed voices when they’re near it, as if in reverence — or fear of disturbing it.

On this chilly Halloween morning, Bob Thicksten has assembled his crew for an “engineering run” on the telescope. The moon is round now, which makes for poor seeing, so the next three nights can be sacrificed in order to take out the mirror and wash it, a job that’s done about twice a year. But this run is unique, because the crew will be removing the 12 pinch levers that surround the mirror and squeeze it to correct for an astigmatism, an imperfection that was there originally.

The mirror also has a slight structural law about a foot square, but nothing can be lone about that. And in addition to several small holes that were the result of bubbles n the molten Pyrex, there’s a three-inch-long gouge in the mirror that seems to have been caused by a wrench being dropped into it. A day earlier, during a staff meeting n which procedures for the engineering run were reviewed, the subject of this gouge came up. Thickscen remarked that he was concerned about it. The dozen or so men and one woman all looked at each other with darting smirks. “That must have happened before any of us got here,” said one. “Yeah, it must have been one of those astronomer-types that did that,” offered another in mock earnest. When I asked Juan Carrasco if he had heard about a wrench being dropped onto the minor, he said he thought someone might have dropped a flashlight once, “but the mirror cover was closed then.” The mirror cover consists of 16 heavy steel leaves that close over the mirror like an iris. Nobody will own up to knowing anything about the gouge.

At 7:20 a.m., a group of plaid-shined men, the “electronickers,” begin removing a spectrometer from the Cassegrain cage, which hangs on the lower end of the telescope, beneath the primary mirror. (Guillaume Cassegrain was the French physician who in 1672 invented the system whereby light is reflected from the primary mirror up to a secondary minor, then back down through a hole in the center of the primary minor.) The Hale’s Cassegrain cage has various electrical assemblies attached to it, and these will be removed as pan of the engineering run, requiring a rebalancing of the telescope.

One of the first jobs on the detailed checklist used by assistant superintendent Merle Sweet is to tie down the telescope and its massive yoke. “Once we take the weight off the telescope, it could flop around,” Sweet explains. At 7:40, with the spectrometer unbolted and moved away, two men are sent up a steep steel ladder to place large pins in the horseshoe bearing. Two other men arc raised on a manlift to the top of the minor cover and proceed to secure the telescope, which is pointing straight up, by lashing it to the yoke.

The men are having trouble aligning a tie-down bar, so another worker walks over to a large telescope control panel situated beneath the horseshoe. This was the night assistant’s duty station when the telescope first came on-line. He presses a button to rock the telescope a fraction to the south. Too far; the men on the minor cover still cannot correctly position the tie-down bar. Merle Sweet, standing on the west side, yells, “Move it one RCH nonh!” Another tweak of a button, and the tiedown bar lines up.

Standing at the control panel is Bruce Baker, who could be mistaken for Kurt Bevacqua — dark-haired, with an 18905-style mustache. Before him are the analog readouts, toggle switches, the six control buttons, various gauges, and a sidereal-time clock. (The telescope operates on star time, not solar time. The sidereal day — the amount of time it takes the Earth to complete one rotation, relative to the stars — is 23 hours, 56 minutes, and 4.09 seconds.) Baker looks over the old control panel and remarks, “This was used back in the days of real astronomy, when it was ten degrees down here.” It can still reach ten degrees inside the dome at night, but the telescope operator now sits in the toasty data room. “Real men observe in the cold," Baker chortles, envisioning a bumper sticker that might have been attached to a ’56 Hudson.

After the telescope is tied down, the men on the mirror cover rotate four rods down from the machine’s steel skeleton and attach them to the Coudt pedestal that juts from the center of the primary mirror. This pedestal holds the main Coudt mirror when it is pivoted down, which isn’t very often these days. One of four different set-ups for focusing light, the Coudt arrangement employs five mirrors and is called into service only when astronomers require a long focal length. The resulting image, which is very large (the full moon ends up six feet across), is reflected into another room.

Meanwhile, two men and a woman are near the west wall of the dome, rinsing natural sea sponges in distilled water in preparation for cleaning the mirror. Bob Thicksten is hoping it can be washed today, but it depends on how the pinch-lever removal goes. When the mirror’s reflective aluminum surface was renewed last June, one pinch lever was taken off to check its condition. Thicksten says the lever was so seized-up that he concluded the levers had not been refurbished since they were installed almost 40 years ago and had long since stopped performing their job of correcting the astigmatism. At one time, the mirror was regularly washed without being removed from the telescope.

According to Luz Lara, who has worked at Palomar for 34 years, they used to tilt the mirror at about a 45-degree angle in order to wash it, which meant that much of the runoff water seeped around the pinch levers. Now, with all the advancements in seeing and the advent of more sensitive instrumentation, the astigmatism and the pinch levers have to be fixed.

By nine o’clock, the Cassegrain cage has been removed, and some of the workers are already trying to muscle off the frozen bolts that attach the pinch levers to the mirror’s steel shell. Thicksten calls a 30-minute break, and two of the workers, Bruce and Dana Cuney, invite me over to their cottage for a cup of coffee.

Exiting the twilight and cold of the dome into the piercing sun and wind outside brings on an eyeache. Cedar trees to the west have been topped to prevent wind turbulance around the dome. Now the wind hits full-on and rolls over the dome’s rounded surface. To the east is a large meadow of ferns, which the telescope’s designers believed had a calming effect on this 5650-foot-high aerie. This time of year, the ferns are coppery and dry and seem to sigh in the breeze. The pines whisper; the cedars moan. Curled leaves rattle on the narrow road that descends a few hundred yards to the Cuney home.

Two curmudgeonly geese in the back yard honk greetings. The two-bedroom cottage would fit unnoticed in Normal Heights, except for the sprawling yard with its apple trees — and the rent. The Cuneys pay a token amount, just over $200 a month, to their employer and landlord, the California Institute of Technology. They’ve lived here 11 years.

Bruce and Dana were construction painters in the San Diego area until hard times hit the business in the late 1970s. They were hired at Palomar partly because Bruce and Bob Thicksten were childhood friends who had grown up next door to each other in a neighborhood called Tortilla Flats, east of I-5 in Leucadia. Bruce, a lean 42-year-old with a friendly mustache, says he’d like to stay up here another ten years. Unlike his wife Dana, who drives down the winding “Highway to the Stars” two or three times a week for supplies and to work out in a gym, Bruce almost never leaves the mountain. “I love it up here," he remarks. “I can do this kind of work all day.”

Dana says that when they first moved to Palomar, friends visited more often than they do now. The residents have become a kind of isolated colony. Several people, including couples, have not been able to live with the solitude and returned to more settled territory. “You either handle it or you don’t,” Dana observes.

Most of the people living at the observatory are there because they revere the place. Luz Lara, who was hired by Palomar’s first superintendent, has seen five others come and go in his 34 years on the job. One of the newer hires, Jeff Phinney, has commuted from his home in La Mesa for the last five years. It takes two cars; when one breaks down he switches to the other. (“It drives my insurance man crazy, always switching the policy back and forth.”) Like many of his co-workers, Phinney first became intrigued with Palomar after he spent time there in sixth-grade camp. After applying to work at the observatory in 1979, Phinney spent the next six years pestering Thicksten for employment. “Persistence got me the job,” he declares.

People tend to like the place so much that when Andath Bitdsell retired in October as the cook at the monastery, the lodge where the astronomers eat and sleep, she was kidded about not pulling the same stunt Chuck Beishline did when he retired from the wood shop. “We gave him a big going-away party, with a cake and everything,” says Russ Day, “and then on Monday morning, he showed up for work at his usual time.” Chuck just kept on doing the same job he retired from, but as a private contractor.

In the Cuneys’ living room, conversation turns to the many parties that have been thrown on the mountain. Sometimes the workers and their guests fire up one of the smaller telescopes (there are five at the observatory) and look at the moon or planets. Few of them have ever looked through the 200-inch. In 13 years, Bob Thicksten says he’s looked through the Hale twice. Bruce Cuney has looked through the east arm focus, which is located in the east arm of the yoke, and seen the moon in such detail “it was like traveling over it in a spaceship.”

The astronomers themselves aren’t averse to cutting loose on the mountain, even though alcohol has been banned from the monastery for years. One group of funsters was known as “Sir Alec Boxenburg’s Flying Circus.” Based at the Royal Greenwich Observatory in England, this bunch used to bring up cases of beer with them, and rumor has it that on nights when the seeing was terrible, they’d end up throwing their empty cans out the slit of one of the domes. The group that Ardath Birdsell calls “the I-talians” were almost as madcap. “Those guys just could not drive," Ardath told me, laughing. “Every time they came up here, they wrecked a car."

Back inside the dome, Jeff Phinney is rinsing out sponges and readying chamois skins for the mirror-cleaning job. “People think we use super-duper high-tech stuff around here,” he cracks. “Look at this.” He shows off the two ancient bottles of Wildroot cream hair tonic the crew keeps on hand for old time’s sake. In an earlier epoch, they used this white, oily goop to clean the mirror before restoring the aluminum finish. Now they use Orvus soap, which contains no additives.

By 11:30, two of the pinch levers are still hopelessly frozen in place around the mirror. Until the levers are removed, the mirror cannot be unbolted from the telescope and moved into position for washing. Thicksten is feeling pressed. He’d hoped that the job would stay on schedule so that several of the workers could attend the wedding of a local rancher on Saturday, rather than put in overtime in the dome. Palomar Plating in Escondido is standing by, ready to sandblast and re-plate parts of the levers, but they’re obviously not going to receive them in the early afternoon, as planned.

As the men keep yanking and banging on the stuck bolts, Earle Emery arrives. For the last 15 years, the Caltech engineer has trekked down from Los Angeles to oversee the washing of the mirror and the re-aluminizing process. He says when the mirror is dirty, the amount of light it reflects drops from about 94 percent of capacity to about 86 percent. A quiet man who clearly enjoys these excursions to the mountaintop, Emery smiles a lot as he thoughtfully answers questions. He says that even though there are three or four eight-meter reflectors planned for telescopes all over the world, Palomar’s 200-inch (a five-meter reflector) will never become obsolete. “Big telescopes essentially last forever,” he explains. “In 20 or 30 years, it’ll probably be killed by light pollution. But it will never be obsolete.”

The Hale is currently the largest working telescope in the world, but that claim to fame will not hold for much longer. There is a bigger telescope operating, the 236-inch Bolshoi Alt-azimuth Telescope in the northern Caucasus Mountains of the Soviet Union, between the Black Sea and the Caspian Sea. But it has been plagued by technical problems. And American engineers are working on a 256-inch mirror for the University of Arizona’s Multiple Mirror Telescope on Mt. Hopkins, in southeast Arizona. For this telescope, they are using techniques that allow single glass mirrors to be cast much thinner and lighter than the Hale’s 200-inch version. The University of Arizona is also planning a 315-inch reflector at Las Campanas in Chile.

But the project that Caltech astronomers are most excited about, and the object of mirror-envy all over the scientific world, is the ten-meter, 394-inch W.M. Keck telescope on the big island of Hawaii. The Keck reflector, which saw its “first light" on November 24, consists of 36 asymetrical mirrors that form a concave, six-sided mosaic. Each of the mirrors is adjustable, and the reflector will have four times the light-collecting area of the Hale. The telescope is located near the 13,796-foot summit of Mauna Kea, considered by many to be the best possible location for looking 15 billion years into space, three-fourths of the way back to the Big Bang.

At about 2:30, big bangs are echoing around the inside of the dome, as Luz Lara uses an impact wrench to remove the bolts that fasten the primary mirror to the bottom of the Hale telescope. A couple of the pinch lever bolts finally had to be broken off. Seven men have pushed out a huge platform on steel rails sunk into the floor and lined up the platform under the mirror. Heavy screw jacks on the platform spin slowly to raise it up into position to cradle the mirror. When the bolts are all removed, Thicksten uses a switch to begin lowering the reflector. He inches it down, stops, checks clearances, inches it down some more. Suddenly he stops and looks at his watch. It’s 2:50 p.m. He turns the controls over to Merle Sweet, saying, “Take over. I’ve gotta go pick up my kids.” Thicksten leaves for the elementary school less than a mile outside the observatory gate.

Sweet finishes lowering the mirror onto the platform but won’t move it to the cleaning station against the west wall until Thicksten returns. By 3:05 Thicksten is back, and eight men and Dana Cuney lean into the platform, rolling it toward the wall and the waiting sponges. When it’s in place and surrounded by steel walkways, everyone comes up to inspect it.

The massive concave disk is colored a dull amber by dust and pollen. Four oil blotches mar the smooth surface, and a couple of whorls in the dust mark places where large moths or bats banged against the starlight. There’s a two-inch ding chipped off one edge. The gouge that no one knows anything about consists of three small smiles nicked into the glass, where something heavy definitely bounced. Numerous black drill holes mark places where bubbles caused imperfections; two more were drilled at either end of a long crack to make sure it stopped. For 20 years, Caltech engineers analyzed photos taken of this crack each time the mirror was washed to determine whether it was growing. It never changed.

As two young post-graduates in astronomy gape at the reflector, Bob Thicksten reminds everyone to take off their hard hats when they’re near it. Something that doesn’t need words is understood, a kind of honor in being entrusted with one of mankind’s most precious tools.

As workers continue to remove portions of the pinch levers that couldn’t be reached before, Luz Lara stares, hypnotized. Lara started working at Palomar for $1.25 an hour in the late 1950s, when he couldn’t speak a word of English. He says that 16 inches of rain fell annually on the mountain then, and all the local streams flow year-round. Now everything is dry, and there is no rain to keep the air clean, so the minor gets dirtier than it used to. He’s mainly the groundskeeper, but his welding skills are legendary, and his steel handiwork is visible in the catwalks he created that give access to the east and west arms of the telescope yoke. (His wife’s chile rellenos have also become legendary among the astronomers she cooks for at the monastery.)

Lara, whose father was a gold miner in Guanajuato, never went to school before he had to take classes to become an American citizen. But in a building crawling with PhDs, Lara usually handles the most delicate job in the cleaning process — going out to the center of the mirror and installing a heavy cover and bolted ring. If he drops one of the pieces, disaster befalls the astronomical world. “I’ve never had a single accident," he reports. “It’s because I care for this as if it were my own, I love it.” Thicksten calls across the mirror to tell Lara to start unbolting one of the disk’s earthquake supports. It’s nearing four o’clock, and the pinch levers still aren’t all removed.

The next morning dawns cold and blustery. In the data room the wind speed is reading 25 miles per hour, and the outside air is four degrees centigrade. As the crew sits around drinking coffee, Bob Thicksten rubs his hands ruefully and mumbles about the cold affecting his arthritis. He’s not in a great mood. “Well, we slipped a day," he declares. The pinch levers didn’t leave the mountain for the plater until five o’clock last night, too late to start washing the mirror. It was pushed back under the telescope for the night. After covering a few details about the day’s work schedule and asking for volunteers to put in overtime, Thicksten sighs, “Wellllll — let’s do it to it.”

The mirror is pushed back to the washing station, and Earle Emery oversees the taping of a plastic skirt around the outside rim. The first task is to daub up the oil spots. Emery dispatches Russ Day for some acetone and another solvent called cyclohexane.

Everybody has a different theory about where the Mobil Flying Horse telescope oil is leaking. Thicksten thinks it’s coming from the drive mechanism in the west arm; somebody else believes it’s dripping from the prime focus cage, near the top of the telescope; another origin might be the counterweight assembly on the east arm. Emery climbs into a long, narrow gangway that is rotated out over the mirror by means of a hand crank. He dabs at the oil spots with tissues soaked in alcohol. He switches to acetone and then to cyclohexane, and a little after eight o’clock he’s cranked back off the mirror.

Before the actual washing can begin, Luz Lara must be moved out on the gangway to the 40-inch hole in the center of the mirror to install a heavy steel plug. His face is serious but calm as he lifts the plug off the boom in slow motion and moves it out over the mirror. Everyone stops for a moment and watches as he carefully lowers the piece into place. Once it’s secure, the mood seems to brighten among the mirror washers.

At about 9:30, Lara starts squirting a hose across the mirror. As the little waves of water slurry toward a hole in the center plug, Thicksten asks Lara not to squirt so hard. “Just let it flow.” With the first layer of dust washed off, the mirror suddenly looks like the famous reflector of the Big Eye of Palomar. Viewed from high up on a narrow catwalk behind the horseshoe, it shimmers like a coin, a four-bit piece flipped to the Earthlings by Zeus himself.

Down beside the mirror Bob Thicksten is watching with an odd expression. “You never get used to it," he remarks, staring at the shimmering icon. The sense of high purpose that permeates the frigid air is not solemn, but almost euphoric. “So many emotions,” Thicksten continues. “You’re keeper of the watch of a tremendous instrument. It’s like taking care of Yosemite — it’s bigger than life. It’d be almost like a sin if we didn’t do it right."

Thicksten-grabs a bucket filled with distilled water and Orvus soap and begins squeezing spongefuls onto the mirror. He’s joined by his secretary, Gail Sibert, who usually helps out on these operations, and Emery. The white soap oozes down toward the center. Gail cranks Jeff Phinney out to the center plug, and he squats there squeezing soap and dabbing at the smooth glass surface. In a free moment, he locates the signature of the chief optician who oversaw the years-long process of grinding the glass to as perfect a parabola as was possible in the 1940s. The name is scratched into the flat rim that surrounds the center hole: Marcus H. Brown 3/1947 A.D.

The mirror is soaped and rinsed twice, then soaped again. Buckets of distilled water are used for the final rinse, so that no minerals are left on the glass. At 10:35, Thicksten, Emery, Phinney, and Sibert begin laying chamois skins on the wet surface. When they’re finished, the mirror gleams with an unnatural clarity, and its imperfections are prominent. The crack, the ding on the comer, the gouge, the black drill holes. A dumb question occurs to me: What if the light from a star an astronomer is looking at happens to fall directly onto one of those holes? I am politely set straight: Starlight does not fall as a point, it spreads out evenly across the glass.

As workers and visitors admire the freshly washed face of the universe, someone mentions how priceless it is. Another recalls the story of the mirror at the McDonald Observatory in the Davis Mountains of Texas. Some years ago, a technician, enraged at being fired, emptied his six-shooter into the mirror. The company that insured the mirror had it surveyed and found that the dings caused by the bullets reduced the minor’s reflectivity by only one percent. So the company paid off one percent of the insurance policy.

Thicksten calls a coffee break, giving Russ Day a chance to take me on another excursion inside the dome. It starts on a steep ladder near the north wall, and as we climb higher, the ladder arches over and becomes a stairway. When the stairway levels out into platform, we are at the ceiling of the seven-story dome, looking down into the telescope. From this height, the mirror still appears large and strangely powerful, as if light were pouring out of it, not into it. We pass through a hatch in the dome, worm our way among heavy beams, then pop out into the sun and wind onto a platform on the dome’s roof.

The gusts tear ferociously at us as they strike the dome and then boil upward. Day almost has to yell in order to be heard. He used to eat lunch up here, “until figured out the light was too bright!” he shouts.

Our tiny platform is at the top of the two gigantic curved slices of dome that slide apart to allow the telescope to peep at the sky. The ends of these structures are covered in silver reflecting tape, to help deflect heat. The light bouncing off the silver surrounds us in radiance. We are standing above the wispy clouds that zoom across the mountaintop, shredding themselves on the crowns of trees and mottling the morning light. Subdued fall colors peek in and out through the clouds, and the bright white domes of Palomar’s four other telescopes wink through the leaves. Beneath our feet, the dome falls away as steeply as a cliff. Day points to the small railing that hugs the smooth surface a few inches below the platform. “The last-chance rail!”

This secret platform, one of a dozen in the dome, would make for perfect trysting. Day doesn’t know if anyone has used it for that, but Thicksten has slept here overnight, with his binoculars. In the singular darkness of Palomar, the Milky Way curves over the dome like spun platinum. It has been the Hale’s inseparable companion for 40 years. The daytime sky is usually a soft blanket of blue, tucked under the chin of the slumbering star-catcher.

This scene of rushing beauty stretching out to infinity could be one of the telescope’s dreams. If so, I’d hate to meet its nightmares.

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