USE OF THE CELESTIAL GLOBES. 



To prepare the globe for use, let small marks (bits of paper 

 gummed on will answer the purpose) be placed upon it, to indi- 

 cate the positions of the sun, moon, and planets, at the time of 

 observing the heavens. The place of the sun on the ecliptic is 

 usually marked on the globe itself. If not, its right ascension 

 (that is, its distance from the vernal equinoxial point, measured 

 on the celestial equator), and its declination (that is, its distance 

 north or south of the equator), are given in the almanac, for 

 every day. The moon's right ascension and declination are likewise 

 given. 



35. To find the place of an object on the globe when its right 4 

 ascension and declination are known. Find the point on the 

 equator where the given right ascension is marked. Turn the 

 globe on its axis till this point be brought under the meridian. 

 Then count off an arc of the meridian (north or south of the 

 equator, according as the declination is given) of a length equal 

 to the given declination, and the point of the globe immediately 

 under the point of the meridian thus found, will be the place of 

 the object. By this rule, the position on the globe of any object 

 of which the right ascension and declination are known, may be 

 immediately found, and a corresponding mark put upon it. 



To adjust the globe so as to use it as a guide to the position of 

 objects on the heavens, and as a means of identifying the stars and 

 learning their names, let the lower clamping- screw of the meridian 

 be loosened, and let the north pole of the globe be elevated by 

 moving the brass meridian until the arc of this meridian between 

 the pole and the horizon be equal to the latitude of the place of 

 observation. Let the clamping-screw be then tightened, so as to 

 maintain the meridian in this position. Let the globe be then so 

 placed that the brass meridian shall be ^ directed due north and 

 south, the pole being turned to the north. This being done, the 

 globe will correspond with the heavens so far as relates to the poles, 

 the meridian, and the points of the horizon. 



To ascertain the aspect of the firmament at any hour of the 

 night, it is now only necessary to turn the globe upon its axis 

 until the mark indicating the place of the sun shall be under the 

 horizon in the same position as the sun itself actually is at the 

 hour in question. To effect this, let the globe be turned until the 

 mark indicating the position of the sun is brought under the meri- 

 dian. Observe the hour marked on the point of the equator which 

 is then under the meridian. Add to this hour the hour at which 

 the observation is about to be taken, and turn the globe until the 

 point of the equator on which is marked the hour resulting from this . 

 addition is brought under the meridian. The position of the globe 

 will then correspond with that of the firmament. Every object on 



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