The policy of the observatory is that of the late George Ellery Hale, its founder Dr. Hale was a man who liked amateurs. The observatory's policy is to admit the public ungrudgingly, up to the point where this begins to interfere with the astronomical research for which the observatory was built.

Obviously not all of the observatory can be shown to tourists, since they arrive at a rate of 100,000 a year. Some of the tourists, however, are amateur astronomers. Cannot at least these be shown the whole installation? Unfortunately if only 1,000 amateurs arrived at Palomar every year, wishing to be shown everything and to talk with the staff, this might interfere with the astronomical work more than the visits of 99,000 tourists.

So the amateur astronomer should not count on seeing more than the most interesting third of Palomar-the mounting and tube of the 200-inch telescope. He will not see the interesting rabbit warrens on two broad floors beneath the observing floor of the 200-inch. The present article therefore will attempt to describe this forbidden region. Nowhere has it yet been systematically described with plan diagrams.

The visitor enters the dome where Russell W. Porter has lettered in the words "Public Entrance" in the drawing labeled "Ground Floor Plan" at left. In vestibule 18, after examining a bronze bust of Dr. Hale, he will turn to the left and climb 26 feet in two flights of stairs, emerging 5,572 feet 6 inches above sea level in the ample visitors' gallery. This is a completely enclosed area of the concrete main observing floor.

Here in full view, only 40 feet away from the gallery, stands the 200-inch telescope. It towers so high that the visitor feels he is almost under it. This vantage point, however, offers the best view K of the telescope.

Visible from the visitors' gallery is the short stairway approach to the coudé spectrograph room shown at 1 in the drawing labeled "Observing Floor Plan."

The room also appears in the elevation drawing below. What appear to be stairs in this room are concrete platforms, each 22 inches higher than the last. This large room will eventually contain four Schmidt spectrographs which are now being made.

The optical train from star to spectrograph film is as follows: to the 200-inch mirror; thence upward to a hyperboloidal convex secondary mirror near the top of the telescope tube; thence downward to a flat mirror opposite the declination axis; thence diagonally downward through the hollow polar axis south bearing (indicated as P.A. on the elevation drawing); next, to a collimating mirror near the exterior wall of the spectrograph room; thence by reflection back to a diffraction grating near the port through which the beam entered the room, thence back to the left through the correcting plates of any chosen one of four large Schmidt cameras (which have 20-inch, 30-inch, 36-inch, and 48-inch primaries); thence to the Schmidt primaries; and finally to the photographic film at the Schmidt focus. With the faintest stars the spectra will be spread to only one inch in length, on the brightest stars to an equivalent length of 12 feet.

At 2 on the observing floor plan is a small automatic elevator that gives the staff quick access to ground floor, mezzanine, observing floor, and balcony.

At 3 is a plate-change room and at 4 is a rest room.

At 5 is a repair shop. Backing it up is a machine shop at the nearby observatory power house, and the larger shop on a the California Institute of Technology campus in Pasadena.

At 6 is the visitors' gallery.

At 7 is the computer. It stands on a raised platform near the right ascension drive. A coffin-like box that encloses it protects delicate mechanisms which change the speed of the sidereal drive] to compensate automatically for angular variations if atmospheric refraction, structural deformations of the telescope. errors in the gears and elsewhere. The box also contains an automatic mechanism for keeping the dome opening in line with the telescope.

At 8 is the double south pier of the telescope (see elevation drawing).

At 9 is a hydraulic hoist also shown in the elevation. This is for raising equipment to the Cassegrain focus of the telescope, also as a working platform.

At 10 is a broad-gauge railroad track on which the aluminizing chamber unit may be drawn from its storage position at the side of the floor to the center under the mirror.

At 11 is the complex control desk.

At 12 is the double north pier of the telescope.

At 13 is the dome balcony, which rotates with the dome-so smoothly that riders on it, not realizing they have been put in motion, exclaim, "The telescope is turning!"

On finally leaving, the visitor will pass the mezzanine floor, perhaps without being aware that it is there. In the vestibule on the ground floor he may not even note an inconspicuous door leading to the ground-floor spaces. No door is shown on the plan drawing; but the door that is there is a fact, not a theory, and it is kept locked. However, for the purpose of this itinerary, let us not descend from the visitors' gallery but, instead, use Porter's master key to all the locks at Palomar, and walk to the observing floor through a door in the side of the gallery. Then:

At 1 is to be a physical-measurements room.

At 2 is an automatic elevator.

At 3 are switchboards for the main electrical distribution. There are also transformers, motor generators, and a battery-charging panel.

At 4 is the constant-frequency room. Here the electric drive of the telescope is initiated and controlled in frequency by a vibrating-string Warren time standard within an accuracy of less than one tenth second a day. On a central table stands a metal tripod a foot high. From it is suspended a wire a few inches long and held taut at the bottom. Attached crosswise halfway up the wire is a small permanent magnet, one end of which projects into a pickup coil connected to the grid of a vacuum tube, the other into a driving coil connected to the plate of the same tube. The wire is tightened from below to vibrate at 60 cycles per sidereal second. The current generated by this unit, its blurred bowstring vibrating softly throughout the night, is amplified to run the one-twelfth horsepower driving motor of the telescope.

At 5 is the storage battery room. If the Diesel motor generator at the observatory power plant should fail, the batteries would automatically take over. (There is no power-line connection between Palomar and the outside.)

At 6 are the telescope relay panels, a maze of apparatus.

At 7 and 8, opening only on the outside stairway to the visitors gallery, are rest rooms.

In the open on the same mezzanine floor are the oil tanks and pumps that constantly force lubricating oil compounded with rust inhibitor, at the rate of two and a half gallons a minute and at 290 to 518 pounds per square inch pressure, through the oil pads of the telescope bearings, so that the telescope floats on a .003- to .005-inch-thick film of oil.

Finally we come to the ground floor where the astronomers work and rest.

Room 1 is for storage.

Rooms 2 to 7 are astronomers' working offices.

Room 8 is for physical measurements.

Room 9 is for photographic developing.

At 10 is the elevator.

At 11 and 12 are large and wonderfully equipped darkrooms.

At 13 is the ammoniating room for plates, and Room 14 is for plate storage.

At 15 is the fan room with air-conditioning machinery, a refrigerating compressor (120,000 B.T.U. per hour) .

Room 16 is to be a chemical laboratory, and Room 17 a physical laboratory.

At 13 is the entrance vestibule.

At 19 is a rest room.

At 20 is the staff's library.

At 21, spacious and comfortable, is the lounge, an all-night clubroom for relaxation between astronomical labors aloft and for conversation.

The fabricated steel telescope base frame (see ground floor plan) is 78 1/2 feet long, 35 1/2 feet wide and 22 feet high (the measurements are made over beam centers). It resembles a span from a through-type railroad bridge, and a check shows that it is about five feet wider and five feet lower than such a bridge.

It is fun to crawl from the adjacent storage space back into the dusty, dim places behind and beneath this base frame, explore its legs, and study the provision for adjusting the telescope in altitude and azimuth. Since several to whom these outsized adjustments were described have suspected that their own legs were being pulled ("Too big a telescope for that sort of thing"), Russell Porter was invited to make a plan and elevation drawing of the adjusting facilities.

The arrangements differ in no basic way from those under amateurs' telescopes. For azimuth adjustment there is a 12-inch pivot ball at the southwest corner of the base frame, and under the remaining corners are 24-inch rolling balls of tool steel. For altitude adjustment there are jacks and wedges. Only one half of the 12-inch pivot ball is needed or used (see drawing), while the 24-inch rolling balls, since they need roll only an inch or so, are cut away to posts six and a half inches in diameter with spherical tops and bottoms.

The base frame is restrained from rolling all over Palomar by the azimuth screw adjustment at the northwest corner of the base frame. Byron Hill, the superintendent of construction at Palomar, says it was easy with his transit to spot the base frame at the outset within one minute of arc of the earth's meridian plane (one eighth inch, plus or minus). A long-handled wrench permits 0ne man to move the 1,000-ton weight and complete the adjustment by means of the push-pull screws shown on the plan.

The four base-frame underpinnings rest on concrete piers in holes excavated 25 feet in the Palomar granite. This was done in order to diminish transmission of vibrations from the piers of the dome which are only four feet deep.

Suppliers and Organizations

The Society for Amateur Scientists
5600 Post Road, #114-341
East Greenwich, RI 02818
Phone: 1-401-823-7800

Internet: http://www.sas.org/

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