Elementary astronomy; a beginner's text-book (1899)
Holden, Edward Singleton, 1846-1914 · New York, H. Holt and company · leaf 142
asses of telescopes outof two lenses of different kindsof glass close together, as inFig. 67. The light from thestar first falls on a lens of crown- Fig. 67.—The Achromaticglass and after passing through Object-glass. it falls on a lens of flint-glass. The two lenses act like acommon convex lens in… … 122 ASTRONOMY. lenses. The telescopes now in use are practically as per-fect as they can be made from the glass we now have. Light-gathering Power of a Telescope.—It is not merelyby magnifying that the telescope assists vision, bat also byincreasing the quantity of light received from any…
Astronomy
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