JF Ptak Science Books Quick Post
I found this illustration browsing Owen Gingrich's (editor) Astrophysics and twentieth century astronomy (Cambridge 1984) , and found it fascinating. The telescope was designed and built by Andrew Ainslie Common (1841-1903, a wealthy engineer and amateur astronomer), and it was a 155 cm/5-foot reflector, and had a flotation mounting. This sort of mounting seems at least unusual to me, though one of Common's earlier telescopes used a mercury flotation system. It was finished in 1889 and replaced a very fine 91cm instrment, both of which were constructed mostly for astrophotographical service. The 155cm didn't really perform, ever, whereas the earlier and smaller instrument certainly did. (Following its service with Common, the 91cm went on to Edward Crossley in 1885m and was then used by James Keeler in 1893, and then by Charles Perrine.) I found the large-ish reservoir in use for keeping stutter and vibration away from the telescope to be very intriguing. It was purchased by Harvard University around 1905, and was moved and again a flotation mounting was employed. (The article on the telescope's purchase is located below, taken from the Harvard Crimson of 5 April 1905.)
"The new 60-inch reflecting telescope, made in England in 1888 by the late A. A. Common and purchased this year by the university, is now being set up at the Astronomical Observatory. A two-story building, 15 feet wide and 27 feet long, has been erected to enclose it. The lower floor contains a silvering room; in the upper room, in which the observer sits, is located the eyepiece of the reflector. The telescope will be adjusted by electricity, and in order to secure a delicate balance a large part of its weight will be floated in a concrete tank, constructed at a cost of $500. In point of aperture the new instrument is the largest telescope in the world. The present plan is to use it for measuring the relative intensity of the light of different stars. It will probably be ready for use early in the summer. [Source: Harvard Crimson.]
(Portrait of Common)
Picture source: Pedro Re," Building Large Teelscopes, Part II: Reflectors", at http://www.astrosurf.com/re/building_large_telescopes_reflectors.pdf
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