Restoration of the 5.0-inch Alvan Clark and Sons Refractor Telescope Tube Assembly Used as a "Finder" Telescope on the Steward Observatory 36-inch Spacewatch Telescope on Kitt Peak -- University of Arizona; Lunar and Planetary Lab; Tucson, AZ / USA


Fig. 1 Photo by Maria Schuchardt, Copyright 2002. All rights reserved.


Fig. 1: The Clark 5-inch telescope "tailpiece" (draw-tube removed). The entire telescope had been painted with white paint and then with a thick outer layer of red paint. Many of us suspected that the finder had to be of Clark manufacture, but the engraved signature was not visible beneath the thick paint layers. When the finder was taken "downtown" to the Lab at LPL, Joe removed the tailpiece and stripped selected areas of the paint with acetone covered with strips of plastic. After the paint layers softened, they could easily be pushed away with a soft polyethylene "scraper" without hurting the polished brass beneath. Once we knew we had a "Clark", we then proceeded with even more care.


Fig. 2: Illustration from the book ALVAN CLARK AND SONS: ARTISTS IN OPTICS, by Warner and Ariail (1995), page 225. Photo reproduced by kind permission from Willmann-Bell, Inc., the publisher. This shows an engraved tailpiece from 1882, not on a five-inch like ours, but on a 6-inch (image rotated CCW, at left, to match the orientation of our tailstock in Fig. 1, and then reproduced aright, at right). The signature, and the placename of "Cambridgeport, Mass.", a neighborhood within Cambridge, MA, are engraved in the same style or hand as our 5-inch. Seeing the similarity of engraving style, and of the hand, gave us further confidence that our "Clark" telescope is authentic.


Fig. 3: An unattributed photo from the Web of a 6-inch Clark, showing a beautifully restored tubework. This is a spare telescope for the other six of the same design that were made for observing the transit of Venus in the 19th Century. This view gave us a suggestion of how our 5-inch tube could look if we restored it. On our tube, Joe stripped the paint and polished the tube with "Brasso" compound at home, using materials selected and very kindly provided by Marcus Perry. Then, Bill Verts polished the tube with Brasso again, slowly turning the tube fitted with end-caps on the longest-bed lathe in the LPL Machine Shop on July 23, 2002. Our tube was then cleaned and given a light protective coat of clear enamel. It should look bright and untarnished for decades into the future.


Fig. 4: Our Clark tube perched on a bench outdoors in Joe's backyard in the hot noonday sun, ready to have a paste-like paint stripper brushed on to soften the two thick layers of paint. The combination of heat and chemical stripper made removing the paint an easy chore.


Fig. 5: A side-view of the still paint-covered tube, under a photometric Tucson sky... . Last chance to see (and photograph) the tube in its old aspect.


Fig. 6: The stripped and polished brass tube of the Clark 5-inch being further polished with "Brasso", in the LPL Machine Shop lathe by Bill Verts. The large lathe had just the capacity to accomodate the long tube (56.5 inches) on its bed: half an inch longer, and the tube would not have fit. Photo by Bob McMillan on July 23, 2002, Copyright 2002, all rights reserved.


Fig. 7: Instrument Maker Bill Verts polishing the Clark tube with Brasso in the LPL machine shop with the tube spinning slowly in the big Sidney lathe (made 7/7/1952: the telescope is more than twice the age of this lathe); Removing the old-age spots of 114 years.


Fig. 8: Showing how the tube is mounted between shop-made end-caps, and to the live-center at the tailstock end. Quite a shine is developing; thanks, Bill!


Fig. 9: Gleam!! The results: The patient has survived the operation and is shown resting, with a new lease on life. Born in the Nineteenth Century, and having worked hard throughout all the Twentieth Century, this Clark is entering the high-tech Twenty-First Century, where it "finds" that its services and companionship are still very highly valued.


Fig. 10: What a beauty... . We've yet to fit some modern eyepieces and a finer reticle, to replace the WWII-era Erfle eyepiece. Stay tuned... .


updated: 2007 Mar. 14 --JLM