Wentworth, G. A. (George Albert), 1835-1906 · Boston, Ginn & company · leaf 173
urface, at theplace where he is, meets the surface of the celestial sphere. The Zenith, Z (Fig. 106), of an observer is that pole of hishorizon which is exactly above his head. Vertical Circles, as NPZS (Fig. 106), are great circles pass-ing through the zenith of an observer, perpendicular to… … Fig. 106 The Ecliptic, A VB (Fig. 107), is a great circle of the celes-tial sphere, apparently traversed by the sun in one year fromwest to east, in consequence of the motion of the earth aroundthe sun. APPLICATIONS 185 The Equinoxes are the points where the ecliptic cuts thecelestial equator. They…
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