Newcomb, Simon, 1835-1909, Holden, Edward Singleton, 1846-1914, joint author · New York, H. Holt · leaf 100
the angle sought. To facilitate the determination of the exact reading ofthe circle, we have to employ special devices, as thevernier and the reading microscope. The Vernier.—In Fig. 3-1, 31 i\7 is a portion of thedivided limb of a graduated circle ; CD is the index armwhich revolves with the… … Fig. 33. 82 ASTRONOMY. the same as that of (n—1) parts on the divided limb M Nor the reverse. The first stroke a is the zero of the vernier, and thereading is always determined by the position of this zeroor pointer. If this has revolved past exactly twenty di-visions of the circle, then the angle…
Astronomy
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