202 RISING, SETTING AND CONJUNCTION OF PLANETS (628 A. D.) has therefore prescribed the use of the true-mean longitude of the planet in the case of Mars, Jupiter and Saturn, and that of the longitude of the planet's sighrocca as corrected for the planet's mandaphala in the case of Mercury and Venus.¹ A rule relating to the distance between two planets which are in conjunction in longitude: 54-55. When the latitudes of the two planets (in conjunction) are of unlike directions, their sum is the (angular) distance between them. When their latitudes are of like direc- tions, the minutes of the distance between them are obtained by taking their difference.² The (linear) distance between the two planets (in conjunc- tion) should be announced by those proficient in the processes of planetary conjunction by taking a minute as equivalent to one-fourth or one-half of an angula, whichever agrees with the phenomenon observed in the sky. According to the commentator Parameśvara, one minute of the distance between the two planets is equal to one-half or one-fourth of an angula, according as the two planets are or are not near the horizon. Brahmagupta has criticised the longitudinal conjunction of the planets. He favours horizontal conjunction which occurs when the two planets are on the same secondary to the prime vertical, because it can be easily observed. Diameters of the planets in minutes of arc: 56. Having (first) divided 32 by 5, divide the same number (i.e., 32) again and again by the same (5) as increased by itself in succession (i.e., by 10, 15, 20, and 25): the results thus obtained are known as the minutes of the diameters of Venus, Jupiter, Mercury, Saturn, and Mars respectively. 1 See Br Sp.Si, ix. 9. Also see SuSi, ii. 56-57;, Sise, xi. 15; and Sisi, II, vi. 20-25(i).
- This rule occurs also in SiDVṛ, I. x. 11; KPr, vii. 8; and has been
quoted by Brahmagupta in BrSpSi, ix 11, and by Sripati in Sise, xi. 18. 3 In BrSpSi, ix. 11-12. Also see Sise, ix. 19-20,
