A popular handbook and atlas of astronomy, designed as a complete guide to a knowledge of the heavenly bodies and as an aid to those possessing telescopes (1891)
Peck, William, Sir, 1862-1925 · New York, G. P. Putnam's Sons · leaf 175
ought to be in the proportion of three to one (see Fig. 42). In the positive eye-piecethe focal lengths of the component lenses are nearly equal, and their curved sides are turned towards eachother as represented in Fig. 42. For low powers and flat fields, the positive eye-piece may be employed… … Fig. 42. eye-pieces.D, Diaphragm. ASTRONOMICAL INSTRUMENTS. Ill 1 1-i 2 2^ 3 ^ 4 5 6 7 8 9 10 4-5 3-9 2-3 1-8 1-5 13 M 0-9 0-8 0-7 0-6 0-5 0-4 In commeucing observations with a telescope, it is advisable that low powers should be firstemployed. These may be gradually increased until the limit…
Astronomy
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