The elements of theoretical and descriptive astronomy, for the use of colleges and academies (1872)
White, Charles J. (Charles Joyce), 1839-1917 · Philadelphia, Claxton, Remsen & Haffelfinger · leaf 48
of a similar character. 42 SEXTANT. THE SEXTANT. 40. The sextant is an instrument by which the angular dis-tance between two visible objects may be measured. It is usedchiefly by navigators; but its portability gives it great valuewherever celestial observations are required. The angles forthe… … of a sector of a circle, the arc of which comprises 60°. A movablearm, CD, called the index-bar, revolves about the centre of thesector. This bar carries at one extremity a vernier, Z>. At theother extremity of the index-bar, and revolving with it, is placeda silvered mirror, C, the surface of…
Astronomy
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