Identifier: adolfostahllectu00astruoft (find matches)
Title: The Adolfo Stahl lectures in astronomy, delivered in San Francisco, California, in 1916-17 and 1917-18, under the auspices of the Astronomical Society of the Pacific
Year: 1919 (1910s)
Authors: Astronomical Society of the Pacific Aitken, Robert Grant, 1864-1951
Subjects: Astronomy
Publisher: San Francisco Stanford University Press
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: MSN

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staff from an early date. The great weight of themoving parts of the telescope had to be considered as well asthe adaptability of the mounting to the various programs ofwork it was hoped might be undertaken. The designs ofmounting and dome finally adopted are, as Mr. Hale puts it,really composite, being the work of Professor Ritchey in theearlier stages and later of Mr. F. G. Pease (who has alsosupervised their erection) ; but doubtless they incorporate alsomany suggestions by Mr. Hale, Mr. Adams and others. Themounting is of what is known as the English type, which hasthe advantage of compactness, and, in view of the great weight(100 tons) of the moving parts, is also, in the opinion of thedesigners, safer than any other type. By way of comparison,it may be noted that the moving parts of the great refractor ofthe Lick Observatory weigh only 14^ tons. The English typeof mounting, however, has the disadvantage that the northernpier prevents the telescope from being turned upon a small
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PLATE LII. The 100-Inch Reflector, October. 1917. The 100-Inch Reflecting Telescope 253 area of the sky centering at the north pole. As the illustra-tion shows, the telescope is hung within a yoke or double fork,which measures 32 feet 8 inches by 16 feet 2 inches. To sup-port the great weight, the system introduced by Dr. Commonwas used, in which the greater part of the weight is taken upby floating the polar axis in mercury. The upper float, on thenorthern pier, carries about 40 tons weight, the lower about 60tons. The instrument is mounted upon a pier of reinforced con-crete measuring 45 by 20 feet at the ground level and 32 feet11 inches in height, raising the center of motion of the tele-scope to a distance of 50 feet above the ground. The top ofthe pier consists of a circular concrete floor 6 inches thick (18inches over the pier proper) and 53 feet 10 inches in diameter.Massive reinforced concrete brackets extending outward fromthe pier on the east and west sides help to support

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