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The Journal of San Diego History
SAN DIEGO HISTORICAL SOCIETY QUARTERLY
Fall 1998, Volume 44, Number 4
Richard W. Crawford, Editor

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Cover photo

Cover Photo [OP15746-1891]
An aerial view of the Hale telescope,
Palomar Observatory.

SDHC photo

[Photo 3545-4] The lead tractor and one of the two trailing tractors hauling the 200-inch mirror up the Highway to the Stars to the waiting telescope in November 1947. The man standing on top of the mirror crate is Byron Hill, the onsite director of construction at the observatory, and later the first superintendent. For much of the journey the visibility was so poor that Hill shouted orders to men on foot to mark the edges of the road for the drivers. The road up Palomar Mountain was designed and engineered so the crated mirrors, and earlier the sections of the telescope mounting, could make the turns.

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[Photo 3545-3] The mirror ready to be backed into the Observatory. This doorway was designed to accommodate the mirror and the components of the telescope mounting. To cross the Galivan Bridge on Highway 101, five miles north of San Juan Capistrano, additional dollies with 16 wheels each were attached to the huge trailer, spreading the 40-ton load of the crated mirror over a total of 58 wheels.

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[Photo 80-1094] The protective covering crate lifted off the mirror. Extraordinary precautions were taken for the journey from the Optical Laboratory at Caltech to the Observatory. The mirror and cell were cushioned with sponge rubber over two I-beams that had been welded to the bed of the trailer. The mirror cell was fastened to the trailer at three points, two fixed and one movable to allow for flexure in the trailer. A radio-crystal detector was mounted on top of the disc to record the vibrations, and connected to an indicator in the cab of the lead tractor. An assistant driver continually monitored the vibrations.

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[Photo 3545-1] The mirror of the 200-inch telescope, in its mirror cell, lifted off the truck at the end of its final journey. The surface is covered with a sheet of paper and a 1-inch thick wooden cover.

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[Photo 80-1096] The mirror, safely on the dolly used to install and remove the mirror from the telescope. The dolly serves as the bottom of the aluminizing tank and is equipped with screw jacks to raise and lower the mirror. In 1947, a fedora was standard headgear for workmen in the Observatory. Today, the Palomar staff members wear hardhats while removing the mirror from the telescope for cleaning or realuminizing; as soon as the face of the mirror is exposed, the hardhats come off, lest a hat fall on the face of the mirror.

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[Photo 80-1082] Electrode holders in the cover to the aluminizing tank. Aluminizing the huge mirror was a formidable challenge. The surface of the disc had to be extremely clean and a very sparse vacuum had to be achieved in the aluminizing tank before the electrodes could be fired. John Strong, the physicist who developed the process, solved the challenge of cleaning the 200-inch mirror by covering the face with Wildroot Cream Oil hair tonic, which was then burned off with heating coils. “In order to get glass clean,” Strong said, “You first have to get it properly dirty.”

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[Photo 82-14275] The beginnings of the construction of the dome, with the completed dome of the 20-inch Schmidt camera, the first working telescope on Palomar Mountain, in the foreground.

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[Photo OP-1560] The steel construction before the top rails were ground smooth for the cars that carry the dome. Byron Hill was given the task of leveling the top rails, using a transit mounted on the rails and working only at night because the daytime sun would heat and expand the steel structure asymmetrically.

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[Photo D1153] The grinding machine used to machine the top railing so there would be no measurable vibration as the dome turned. Outdoors, in inclement weather, this was a formidable machining job.

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[Photo D1148] The cars that carry the weight of the dome on the machined railing. These cars caused incredible problems to the Palomar staff and engineers because of the design of the lubricating systems; a design competition, run by engineers who didn’t have to lubricate the cars, awarded the design a prize. Today, the position of the dome is tracked with barcodes. A portion of the wiring of the dome is visible next to the carriage.

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[Photo D1124] The steel frame of the observatory and dome was erected on the site by Consolidated Steel of Los Angeles. The new Highway to the Stars was not finished, so the trucks carrying the steel had to go up the old Nate Harrison grade on the back of the mountain. One heavy tractor-trailer rig tipped backward on the steep grade. The Palomar staff, who prided themselves in resourcefulness, rescued the tractor-trailer and cargo with a stout chain and an old Caterpillar tractor.

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[Photo 82-14281] The famed Edwin Hubble, with his ubiquitous pipe. Hubble was always eager for publicity, and liked to give the impression that the 200-inch telescope was being built for his research.

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[Photo 82-14262] The dome, closed in. The dome of the observatory was designed and constructed as a welded monococque construction for strength and light weight. Marc Serrurier designed the structure, with advice from Theodor von Karmann and Romeo Martel of the Caltech engineering departments, and from the Goodyear Zeppelin Company. It was the largest welded structure ever built.

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[Photo 82-14305] The optical laboratory. The honeycombed disc in the right foreground is one of the polishing tools. Each square in the honeycomb is a Pyrex block, 4-inches square. These blocks became favorite souvenirs of the project.

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[Photo 80-1092] The back of the mirror cell, showing the mirror-supports in the pockets that were cast into the mirror blank. Each mirror support depends on hundreds of finely machined counterweights, levers, and cams to exert miniscule forces on the back of the mirror as it is moved, compensating for the tendency of the glass disk to sag and deform the shape of the mirror surface. To overcome the stiction in the original mirror-supports, they were redesigned and rebuilt, using carefully selected bushings, and with some of the machined surfaces polished to optical tolerances.

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[Photo 80-1095] A closeup of two of the mirror supports, photographed from the hole provided for the Cassegrain focus of the telescope. The 40-inch diameter glass plug that was used to fill the hole in the center of the mirror while the blank was ground and polished is now on display at the Griffeth Observatory in Los Angeles. The original design for a Cassegrain focus called for an observer’s seat hung from cables, like a child’s swing. The astronomers didn’t like the idea, so a gimballed chair was installed instead; some astronomers got motion sickness from the chair. Today, the Cassegrain focus is used to mount huge instrument packages with ccd detectors, cooling equipment, and optics.

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[Photo 82-14333] [Photo 82-14334] The telescope mounting was shipped in pieces, on three ships, from Philadelphia to San Diego. Westinghouse, like other companies associated with the project, was eager to have their corporate identification prominently displayed on the components they had built.

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[Photo 82-14314] The components of the mounting were pre-drilled for alignment pins in the Westinghouse South Philadelphia factory. The Westinghouse engineers thought it would go together like a giant erector set. The pins did not always align as planned, and much machining and refabrication was done on the site before the mounting was assembled.

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[Photo OP1895] The massive yoke assembly that holds the telescope tube. An opening and ladder leading up into the yoke, visible at the lower left, allows access to the declination bearings, and to the Nasymth focus, which was provided in the original plans, but not used until recently.

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[Photo OP1894] The tube of the telescope under construction. The protective aperture is open above the concrete disc that is substituting for the mirror. The diagonal struts are the famous Serrurier truss, designed by Marc Serrurier to maintain the critical alignment of the two ends of the telescope tube. The Serrurier truss has been incorporated into almost every large telescope, and many small telescopes and other structures built since the 200-inch telescope.

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[Photo 80-1083] The telescope with Byron Hill’s concrete disc mounted for balancing, before the mirror was ready to be brought to Palomar. The aluminizing tank is in the background. When the mirror was installed, the concrete substitute disc was put next to a walkway outside the Observatory, where it sits today. One night during a long observing session, the astronomer Olin Wilson and the night assistant Ben Traxler put a sign on the concrete disc outside:

After a woman fled to the Forest Service office down the mountainside, demanding to be protected from the spacemen, Byron Hill tore down the sign.

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[Photo 80-1093] An observer on the elevator that brings observers to the prime focus cage. Some contemporary cartoonists portrayed the telescope as a carnival cannon and the observers as human cannonballs. One night when the elevator broke just before an observing run, the night assistant loaded a young, willing Allan Sandage into the prime focus by lowering the tube to its limit and letting Sandage climb a rickety ladder. As the telescope slewed up into position for a night of observation, Sandage was a prisoner in the prime focus cage.

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[Photo 80-1080] An observer in the prime focus cage. The original observer’s seat was later replaced with the seat from an old hayrake that had been left around from the days when the Beech family raised cattle on the site of the Observatory. The diminutive Walter Baade, a frequent early observer, claimed that the seat had been modeled from the derriere of Rudolf Minkowski, a huge bear of a man who was a frequent observer in the 1950s.

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[Photo 80-1098] One of the control panels which allowed the night assistants to dial in the coordinates of a star or other object, then push a button to slew the telescope to the selected position. The selsyn-controls were an unprecedented improvement on the positioning equipment used on early telescopes. The beautifully machined drive gears, smooth bearings, and the superb variable-rate clock enabled the telescope to point and track with remarkable accuracy, though nowhere near the accuracy claimed in the early plans that called for an analog computer in the control system. The handset on the control panel allowed the night assistant to speak directly with the observer in the prime focus, the cassegrain focus, or the coud‚ room.

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[Photo 80-1097] The 48-inch Schmidt camera at Palomar, built with funds from the original grant for the 200-inch telescope to provide an instrument for sky surveys. The spherically-ground mirror at the base of the cannon-like tube is 72-inches in diameter. The thin correction plate at the muzzle of the cannon is 48-inches in diameter. The long tube on top of the telescope is one of two guiding scopes, used by the observer to hold the telescope on a guide star for the exposures. The 48-inch Schmidt camera, renamed the Oschin Telescope, was recently upgraded with a new correction plate, enabling photography into the infrared, and is currently in the midst of a new sky survey.

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[Photo OP1890] Russell Porter, who designed the art-deco dome, felt strongly that the dome should be free of excess ornamentation, that the design should express “extreme simplicity along with the appearance of permanency,” and that unlike the dome of the 100-inch Hooker telescope at Mount Wilson, which seems to float above the ground, the dome of the 200-inch telescope should appear firmly anchored to the ground. The aesthetically pleasing proportions and size of the dome, coincidentally almost identical to the dimensions of the Pantheon in Rome, derive from the focal ratio and size of the telescope.

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[Photo 81-12445] The Observatory, with its romantic location on top of the mountain, attracted lovers and honeymooners. Bill Marshall and Sylvia Traxler, who had grown up on the mountain (his mother was the elementary school teacher at the Observatory and her father was one of the first night assistants and later an engineer) were married in the dome of the 200-inch telescope.

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[Back Cover — Photo OP15746] The dome of the 200-inch telescope was originally painted with aluminum paint to reflect the heat of the sun. Today the domes are painted with a bright white magnesium paint for the same purpose. On the ascent of Palomar Mountain, the dome suddenly appears above the trees, like the hills of Jerusalem to a pilgrim approaching from the desert below.

SDHC photo by Larry Booth

Larger image [81k]

 

Photographs are from the Research Archives of the San Diego Historical Society.