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Argo. Thus, for example, we have Argus, which after the subdivision 

 belonged to the constellation Carina. The variable star 7 Argus 

 also belongs to the constellation Carina. But in the case of stars not 

 marked by Bayer, the names were assigned according to the subdivided 

 constellations, Vela, Carina, etc. Confusing though this proceeding 

 may appear to be, it is not productive of serious trouble. The main 

 point is that the same star should always have the same name in 

 successive catalogues. Still, however, it has recently become quite 

 common to ignore the constellation Argus altogether and use only the 

 names of its subdivisions. The reader must therefore be on his guard 

 against any mistake arising in this way in the study of astronomical 

 literature. 



In star catalogues the position of a star in the heavens is sometimes 

 given in connection with its name. In this case the confusion arising 

 from the same star having different names may be avoided, since a star 

 can always be identified by its right ascension and declination. The 

 fact is that, so far as mere identification is concerned, nothing but 

 the statement of a star's position is really necessary. Unfortunately, 

 the position constantly changes through the precession of the equinoxes, 

 so that this designation of a star is a variable quantity. Hence the 

 special names which we have described are the most convenient to 

 use in the case of well-known stars. In other cases a star is designated 

 by its number in some well-known catalogue. But even here different 

 astronomers choose different catalogues, so that there are still different 

 designations for the same star. The case is one in which action of 

 uniformity of practice is unattainable. 



Cataloguing and Numbering the Stars. 



A catalogue or list of stars is a work giving for each star listed its 

 magnitude and its position on the celestial sphere, with such other 

 particulars as may be necessary to attain the object of the catalogue. If 

 the latter includes only the more conspicuous stars, it is common to add 

 the name of each star that has one; if none is recognized, the con- 

 stellation to which the star belongs is frequently given. 



The position of a star on the celestial sphere is defined by its 

 right ascension and declination. These correspond to the longitude 

 and latitude of places on the earth, in the following way: Imagine a 

 plane passing through the center of the earth and coinciding with its 

 equator, to extend out so as to intersect the celestial sphere. The line 

 of intersection will be a great circle of the celestial sphere, called the 

 celestial equator. The axis of the earth, being also indefinitely ex- 

 tended in both the north and the south directions, will meet the celestial 

 spheres in two opposite points, known as the north and south celes- 

 tial poles. The equator will then be a great circle 90° from each 



