Elementary astronomy; a beginner's text-book (1899)
Holden, Edward Singleton, 1846-1914 · New York, H. Holt and company · leaf 102
to any ob-server is a plane that contains his vertical line. It must pass throughhis zenith and nadir, and must be perpendicular to his horizon. Avertical plane cuts the celestial sphere in a vertical circle. * It is, in fact, that point at which the Sun passes the celestialequator in moving1 from… … Fig. 46. As soon as we imagine an observer to beat any point on the Earthssurface his horizon is at once fixed ; his zenith and nadir are also fixed. From his zenith radiate anumber of vertical circles thatcut the celestial horizon perpen-dicularly, and unite again at hisnadir. Some one of these…
Astronomy
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