The geography of the heavens and classbook of astronomy; (1863)
Burritt, Elijah H. (Elijah Hinsdale), 1794-1838, Mattison, Hiram, 1811-1868, Whitall, Henry, 1819-1887? Celestial planisphere. [from old catalog] · New York, Mason brothers; Boston, Mason & Hamlin; [etc., etc.] · leaf 325
Reflector is so called from M. Casse-grain, its inventor. It resembles the Gregorian, except that thespeculum placed in the focus of the reflector is convex instead ofconcave. The Herschelian Reflector differs from all others, in having nosmall reflector whatever ; the light being reflected back to… … Here the concave speculum is seen to be inclined a little to the lower side of the tube,8-> that the parallel rays A are reflected back to the observer at B, at the Fide of theinstrument, where the eye-piece is placed. 706. Cassegranian? Difference? Herschelian? Where 705. Newtonian…
Constellations · Stars
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