A high-school astronomy: in which the descriptive, physical, and practical are combined .. (1853)
Mattison, Hiram, 1811-1868 · New York, F. J. Huntingdon [etc.] · leaf 235
ly-half the distance from B to C. *-£ 531. Reflecting telescopes are of several kinds—viz.,the Gregorian, the Newtonian, the Cassegranian, theHerschelia?i, &c. The Gregorian Reflector has an aper-ture in the center of the speculum, and a small concavemirror in the focus of the speculum, which… … 1 Here the light A falls upon the speculum at B, and is reflected back to the small mir-ror C. by which it is thrown out, through the aperture in the speculum, to the eye ofthe observer at D. The object is supposed to be off on the right, in the direction towardwhich the instrument is pointed. It…
Astronomy
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