PLEASURES OF THE TELESCOPE. 291 



object is concerned, than a larger glass. The larger the object 

 glass and the higher the power, the greater are the atmospheric 

 difficulties, A small telescope will perform very well on a night 

 when a large one is helpless. 



Turn the glass upon /3 (Rigel), the white first- magnitude star 

 in Orion's left foot. Observe whether the image with a high 

 power is clear, sharp, and free from irregular wisps of stray 

 light. Look at the rings in and out of focus, and if you are satis- 

 fied with the performance, try for the companion, A good three- 

 inch is certain to show it, except in a bad state of the atmosphere, 

 and even then an expert can see it, at least by glimpses. The 

 companion is of the ninth magnitude, some say the eighth, and 

 the distance is about 9"5", angle of position (hereafter designated 

 by p,) 199.* Its color is blue, in decided contrast with the white 

 light of its great primary. Sir John Herschel, however, saw the 

 companion red, as others have done. These differences are doubt- 

 less due to imperfections of the eye or the telescope. In 1871 

 Burnham believed he had discovered that the companion was an 

 exceedingly close double star. No one except Burnham himself 

 ever succeeded in dividing it, and he could only do so at times. 

 Afterward, when he was at Mount Hamilton, he tried in vain to 

 split it with the great thirty-six-inch telescope, in 1889, 1890, and 

 1891. His want of success induced him to suggest that the com- 

 ponent stars were in rapid motion, and so, although he admitted 

 that it might not be double after all, he advised that it should be 

 watched for a few years longer. 



Rigel has been suspected of a slight degree of variability. It 

 is evidently a star of enormous actual magnitude, for its parallax 

 escapes trustworthy measurement. It can only be ranked among 

 the very first of the light-givers of the visible universe. Spectro- 

 scopically it belongs to a peculiar type which has very few repre- 

 sentatives among the bright stars, and which has been thus de- 

 scribed : " Spectra in which the hydrogen lines and the few metal- 

 lic lines all appear to be of equal breadth and sharp definition." 

 Rigel shows a line believed to represent magnesium ; but while it 

 has iron lines in its spectrum, it exhibits no evidence of the exist- 



* The angle of position measures the inclination to the meridian of a line drawn between 

 the principal star and its companion ; in other words, it shows in what direction from the 

 primary we must look for the companion. It is reckoned from up to 360, beginning 

 at the north point and passing around by east through south and west to north again. 

 Thus, if the angle of position is or 360, the companion is on the north side of the pri- 

 mary; if the angle is 90, the companion is to the east; if 180, to the south; if 270, to 

 the west, and so for intermediate angles. It must be remembered, however, that in the 

 field of the telescope the top is south and the bottom north, unless a prism is used, when 

 directions become complicated. East and west can be readily identified by noticing the 

 motion of a star through the field ; it moves toward the west and from the east. 



