1919.] Ancient Hindu Spherical Astronomy. 169 
the deferent at intervals of 30 degrees, the corresponding posi- 
tions on the epicycle being B,, B,, B,, ete. The period of 
the planet, and th 
ference of the epicycle is the sidereal year (2). At HA, B, the 
earth, sun and planet are in line: the point B moves from 5, 
to B, while the point A moves from Ap to A, and we have 
angle BA; >; _ 1/# _ 1. in the figure. 
angle A,H A, 1/P, 
From B, to B, the planet retrogrades and the angle of retro- 
gression HZ is in the figure approximately 25 degrees. The 
stationary points are determined by 
Br | EB = (velocity in deferent) / (velocity in 
epicycle) = u/v.* 
* See § 20(a). 
