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Unformatted text preview: Magnifying Power The ability of a telescope to enlarge images is the best-known feature of a telescope. Though it is so well-known, the magnifying power is the least important power of a telescope because it enlarges any distortions due to the telescope and atmosphere. A small, fuzzy faint blob becomes only a big, fuzzy blob. Also, the light becomes more spread out under higher magnification so the image appears fainter! The magnifying power = (focal length of objective) / (focal length of eyepiece); both focal lengths must be in the same length units. A rough rule for the maximum magnification to use on your telescope is 20 D to 24 D , where the objective diameter D is measured in centimeters . So an observer with a 15-centimeter telescope should not use magnification higher than about 24 15 = 360-power. The set of four figures below shows the effect of a larger objective size. They have the same magnification. These are ideal images of two stars separated by 0.5 arc seconds which would be magnification....
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- Fall '10