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
the Herschelian, &cThe Gregorian Reflector has an aperture in the center of thespeculum, and a small concave mirror in the focus of the specu-lum, which reflects the light back through the aperture to theeye-piece. In this way the observer is enabled to face theobject, and to direct the… … 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 of theobserver at D. The object is supposed to be off on the right, in the direction towardswhich the instrument is pointed. It is…
Constellations · Stars
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