photographing stellar spectra, and the results formed the basis of the 

 Draper Catalogue. In 1889 the Bache telescope was sent to Harvard's 

 observatory in Peru for studies of the southern stars. To continue the 

 unfinished studies in Cambridge, Henry Draper's widow provided money 

 for another photographic instrument. This telescope, also made by the 

 Clarks, differed from the Bache telescope only in its slightly longer focus 

 and its German rather than forked equatorial mount. 118 In 1947 the 

 Draper doublet was transferred to an observatory near Torun, Poland, 

 the birthplace of Copernicus. 



For detailed study of the spectra of the brighter stars the Harvard 

 astronomers used the 1 1 -inch photographic telescope which had belonged 

 to Henry Draper (q.v. ). A battery of four objective prisms, each with a 

 clear aperture of 1 1 inches, was constructed by the Clarks for use with this 

 telescope. When all four prisms were used simultaneously the spectral 

 images were over 4 inches long, and, in some cases, showed as many as 500 

 lines. 119 In 1947 Harvard sent this telescope on a long-term loan to the 

 Sun Yat-sen University Observatory, in Canton, China. 120 



Several instruments used in the high altitude Boyden investigations 

 were from the workshops of Alvan Clark & Sons. Perhaps the most novel 

 of these was the visual-photographic refracting telescope. This lens com- 

 bination could be focused for either the yellow or blue rays by altering the 

 direction and position of the crown glass component (see above, p. 000) . 

 Early in 1887 the Clarks made a smaller, experimental model which 

 proved so successful that they received an order for the 13-inch objective. 

 According to E. C. Pickering, both the visual and photographic images 

 formed by these instruments were excellent. 121 The mount which held the 

 13-inch refractor also held a Clark-made photographic doublet of 8 

 inches aperture and 1 1 feet focal length. These telescopes were used at 

 Willows, California, for observations and photographs of the solar eclipse 

 of 1 January 1889; the following year they were sent to Harvard's observ- 

 ing station at Arequipa, Peru. Among the other Boyden instruments made 



118 Annals, Harvard College Observatory, vol. 26, pt. 1 (1891), p. xiii. 



119 Ibid., pp. xv-xvi. 



120 Dorrit Hoffleit, "A Famous Old Telescope Goes to China," Sky and Telescope, 

 vol. 7 (1947), pp. 8-9. 



121 Edward C. Pickering, "New Form of Construction of Object-Glasses Intended 

 for Stellar Photography," Nature, vol. 36 (1887), p. 562. 



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