Jacoby, Harold, 1865-1932 · New York, The Macmillan company · leaf 449
APPENDIX the gnomon to start at 0, and to extend a short distance in the direction OP. Now suppose OIV, situated in the horizon plane NIVS, to be the direction in which the shadow falls at four o'clock. Then, remembering that solar time is simply the hour-angle of the sun, … Fig. 109. The Sundial. also 60°. Now let us consider the spherical triangle formed on the celestial sphere by the three points P, N, and IV. In it we know the side PN, for it is the elevation of the celestial pole above the horizon, and therefore equal to the latitude of the place where the dial is…
Astronomy
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