. Astronomy for students and general readers . Fig. 10.—THE PARALLEL SPHERE. If the observer is at the north pole his zenith and thepole itseK will coincide : half of the stars only will be vis-ible, and these will never rise or set, but appear to movearound in circles parallel to the horizon. The horizonand equator will coincide. The meridian will be indeter-minate since Zand P coincide ; there will be no east andwest line, and no direction but south, The sphere in thiscase is called a parallel ipfiere. DIURNAL MOTION IN DIFFERENT LATITUDES. 27 If instead of travelling to tlie north the obser
. Astronomy for students and general readers . Fig. 10.—THE PARALLEL SPHERE. If the observer is at the north pole his zenith and thepole itseK will coincide : half of the stars only will be vis-ible, and these will never rise or set, but appear to movearound in circles parallel to the horizon. The horizonand equator will coincide. The meridian will be indeter-minate since Zand P coincide ; there will be no east andwest line, and no direction but south, The sphere in thiscase is called a parallel ipfiere. DIURNAL MOTION IN DIFFERENT LATITUDES. 27 If instead of travelling to tlie north the observer shouldgo toward the er[uator, the north pole would seem to ap-proach his horizon. When he reached the equator bothpoles would be in the horizon, one north and tlie othersouth. All the stars in succession would then be visible,and each would be an equal time above and below Fig. 11.—THE EIGHT SPHERE. The sphere in this ease is called a right sphere, becausethe diurnal motion is at right angles to the horizon. If nowthe observer travels southward from the equator, the southpole will become elevated above his horizon, and in thesouthern hemisphere appearances will be reproducedwhich we have already described for the northern, exceptthat the direction of the motion will, in one respect, bedifferent. The heavenly bodies will still rise in the eastand set in the west, but those near the equator will passnorth of the zenith instead of south of it, as in our lati-tudes. The sun, instead of moving from left to right,there moves from right to left. The bounding line be-tween the two directions of motion is the equator, wherethe sun culminates north of the zenith from March tillSeptember, and south of it from September till March. If the observer travels west or east of his first sta-tion, his zenith will still remain at the same angular 28 ASTRONOMY. distance f
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