A beginner's star-book; an easy guide to the stars and to the astronomical uses of the opera-glass, the field-glass and the telescope (1912)
Murphy, Edgar Gardner, 1869-1913 · New York, London, G.P. Putnam's sons · leaf 20
sually classified, as to size, according to the surface diameter of the lens at the large end of theinstrurnent. A 2-inch telescope, and a 3-inch, are telescopes in which these lenses are, respectively, 2 inches or 3inches in diameter. A 2-inch will bear a magnifying power, for the average eye, of… … REGION OF THE DOUBLE STAR CLUSTER (/i,\) IN PERSEUS From a pholonraph taKen at the Yerkes Observatory 6 a BcGinncr0 Star«=Book In at least one other respect the system of mapping here adopted will be of specialservice. The reader is provided not only with a series of Key-Maps on the right-hand…
Astronomy
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