ASTRONOMY. 13 



Suppose the hour according to siderial time, when a 

 star passes the meridian, to be 4 h . 24?i. 5Qsec. 



4h. = 60 

 24,m. = 6 

 50sec. = 12'. 30" 



Right Ascen. = 66. 12'. 30". 



h. The preceding observations, for determining the 

 places of the stars, are all supposed to be made on 

 the meridian ; and such, when they can be ob- 

 tained, on account of their simplicity, are prefer- 

 able to all others. It often happens, however, that 

 the stars must be observed when they are not on 

 the meridian, and their positions, with respect to 

 the immoveable circles of the sphere, must then be 

 derived from spherical trigonometry. 



c. The angle which the meridian of a star makes with 

 the meridian of the place of observation, is called 

 the star's Horary Angte, as it is the angle which 

 measures the time between the instant of observa- 

 tion and the star's passage over the meridian. 



21. Of these five quantities, the Declination, 

 the Altitude, the Azimuth, the Horary Angle 

 of a star, and the Latitude of the place of ob- 

 servation, if any three be given, the other two 

 may be found from the resolution of the spheri- 

 cal 



