PLEASURES OF THE TELESCOPE. 203 



are closest is about 1"7", and when they are widest 6'7". This star 

 is one of those whose parallax has been calculated with a reason- 

 able degree of probable accuracy. Its distance from us is about 

 1,260,000 times the distance of the sun, the average distance apart 

 of the two stars is about 2,800,000,000 miles (equal to the distance 

 of Neptune from the sun), and their combined mass is three times 

 that of the sun. Hall has seen in the system of 70 Ophiuchi 

 three stars of the thirteenth magnitude or less, at distances of 

 about 60", 90", and 165" respectively. 



The star 73 is also a close double, and beyond our reach. Its 

 magnitudes are six and seven, distance 0*7", p. 245. It is, no doubt, 

 a binary. 



Three star clusters in Ophiuchus remain to be examined. The 

 first of these, No. 4256, is partially resolved into stars by the five- 

 inch. No. 4315 is globular, and has a striking environment of by- 

 standing stars. It is about one quarter as broad as the full moon, 

 and our largest aparture reveals the faint coruscation of its 

 crowded components. No. 4410 is a coarser and more scattered 

 star swarm a fine sight. 



Farther toward the east we encounter a part of Serpens again, 

 which contains just one object worth glancing at, the double 6, 

 whose stars are of magnitudes four and four and a half, distance 

 21", p. 104. Color, both yellow, the smaller star having the deeper 

 hue. 



Let us next, with the guidance of map No. 15, enter the rich 

 star fields of Hercules, and of the head and first coils of Draco. 

 According to Argelander, Hercules contains more stars visible to 

 the naked eye than any other constellation, and he makes the 

 number of them one hundred and fifty-five, nearly two thirds of 

 which are only of the sixth magnitude. But Heis, who saw more 

 naked-eye stars than Argelander, makes Ursa Major precisely 

 equal to Hercules in the number of stars, his enumeration show- 

 ing two hundred and twenty-seven in each constellation, while, 

 according to him, Draco follows very closely after, with two hun- 

 dred and twenty stars. Yet, on account of the minuteness of the 

 majority of their stars, neither of these constellations makes by 

 any means as brilliant a display as does Orion, to which Arge- 

 lander assigns one hundred and fifteen naked-eye stars, and Heis 

 one hundred and thirty-six. 



We begin in Hercules with the star k, a pretty little double of 

 magnitudes five and a half and seven, distance 31", p. 10, colors 

 yellow and red. Not far away we find, in y, a larger star with a 

 fainter companion, the magnitudes in this case being three and a 

 half and nine, distance 38", p. 242, colors white and faint blue or 

 lilac. One of the most beautiful of double stars is a Herculis. 

 The magnitudes are three and six, distance 47", p. 118, colors 



