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Elements of astronomy .. (1870)

Brocklesby, John, 1811-1889. [from old catalog] · New York, Sheldon and company · leaf 117

An illustration from Elements of astronomy .., 1870, leaf 117
ecliptic is likewise observed, we have the means ofsolving this problem. It is a law in optics, that the ap-parent magnitude of a body is inversely proportioned toits distance ;l that is if at a certain distance it appears ofa ceitain size, when ten times nearer it will appear tentimes larger, and… … from the eye at C. At the distance CB1 the body A is seen under theangle DCL1 which is 10°. Ten degrees is at this distance its apparentdiameter. At the distance CB which is twice CB1 the apparent diameterof A is LCD, the half of DCL1 or an angle of Jive degrees. Thus the lawis proved. Apply it to…

Astronomy

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