Jones, H. Spencer (Harold Spencer), 1890- · London E. Arnold & co. · leaf 190
on EZ. Suppose the rays 8fi, ZjOcome from two points at the opposite ends of a diameter ofthe Moon: then S/)Zq is a measure of the Moons apparentdiameter as seen by the naked eye. The image of the Moonproduced by the telescope subtends, however, the larger anglesEz. The ratio of the apparent… … NlOKKICS UHSlCK\ATOkV 4O-IMII K KlK Al 11 >K. ASTRONOMICAL INSTRUMENTS 161 therefore the ratio of the focal lengths of the object-glass andeye-piece. If the object-glass has a focal length of 20 ft. andthe eye-piece of ^ in., the magnification will be 480 ; if theeye-piece has a focal length of…
Astronomy
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