THE CELESTIAL LATITUDE OF A PLANET A rule relating to the determination of the time and the com- mon longitude of two planets when they are in conjunction in longitude: 201 49-51. If one planet is retrograde and the other direct, divide the difference of their longitudes by the sum of their daily motions; otherwise (i.e., if both of them are either retrograde or direct), divide that by the difference of their daily motions: thus is obtained the time in terms of days, etc., after or before which the two planets are in conjunction (in longitude). The velocity of the planets being different (literally, manifold) (from time to time), the time thus obtained is gross (i.e., approximate). One, proficient in astronomical science, should, therefore, apply some method to make the longitudes of the two planets agree to minutes. Such a method is possible from the teachings of the precepter or by day to day practice (of the astronomical science).¹ The method to be used here is obviously the method of successive approximations. A rule relating to the computation of the celestial latitude of a planet when it is in conjunction with another planet: 52-53. Diminish the longitude of the planet in conjunc- tion with another planet by the degrees of (the longitude of) the ascending node (of that planet); by the Rsine of that multiply the greatest latitude (of the planet) and divide (the product) always by the (corresponding) "divisor" (defined in stanza 48): thus is obtained the latitude of Jupiter, Mars, or Saturn. In order to find the latitudes, north or south, of the remaining planets (Mercury and Venus), subtraction (of the degrees of the longitude of the ascending node) should be made from the longitude of the planet's sighrocca. The longitude of the planet to be used in the above rule is really the heliocentric longitude and not the geocentric longitude. Brahmagupta ¹ Cf. Br SpSi, ix. 5-6 ; ŚiDVṛ, I, x. 7-9 (i) ; Siśe, xi. 12-13.
- This rule occurs also in SiDV, 1, x. 10, 9 (ii).
