156 Journal of the Asiatic Society of Bengal. [N.S., XV, 
horizon. The circle PGE, passing through the pole and the 
east and west points, is the so-called ‘six-hour circle’ (wn- 
mandala). 
Denoting the radius QO by r we have 
(i) RC = r cos 6, the ‘day radius’ Shaciel eae: 
(ii) CD =r sin 6 tan 9, the ‘earth sine’ (kshitijya) 
(iii) sina, = OD/OF = sin 5/ cos 
(iv) a nd 7 on? (+ tang 
" a where r (1 + tan > tan 6) is termed 
e ‘day measure’ (antya 
(v) sn GCF = cpr = CD/RC =r sin § tan ¢/r cos 6 
an ¢ tan 6, and GCF = Aa is termed 
oe “ascensional difference’ (chara).* 
(6) In figure 2, NES is the horizon, NZMS is the meridian 
(yamyottaravritta), QKE is the equator, ZH is the prime Mine 
cal (samamandala); X is the position of a star, and MXF i 
Fig. 2. 
its arate Mans The angle ZPX=h is the hour angle 
(nata), the are NSH = a is the azimuth, ZXP is the parallac- 
tic angle, NXS i is the so-called ‘circle of position, and NXP 
= € is the aksha valana, or ‘ deflection due to latitude.’ 
(c) In figure 3, QTY R represents the equator and CY L the 
ecliptic (apamandala). The point Y is the so-called ‘first 
* The hour angle ROF = 90° + A a, consequently cosh = —sin Aa 
= — tan > tan 3. ‘ : =! 
