CHAPTER IV TRUE LONGITUDE OF A PLANET Definition of the Sun's mean anomaly: 1. Having applied the correction for the (local) longitude to the mean longitude of the Sun, subtract (therefrom) the longitude of the Sun's apogee (ucca): the remainder is the Sun's (mean) anomaly. In that (anomaly), three signs form a quadrant. That is to say, Sun's mean anomaly (mean longitude of the Sun)- (longitude of the Sun's apogee). The Sun's apogee is the remotest point of the Sun's apparent orbit. Beginning with the Sun's apogee, in Hindu astronomy, the kakṣāvṛtta (deferent or concentric) for the Sun is divided into four equal parts called anomalistic quadrants (pada or päda) and twelve equal parts called ano- malistic signs (rāśi). Thus there are three anomalistic signs in an anomalistic quadrant. The anomalistic signs are given the same names as the signs of the zodiac, viz., Aries (mesa). Taurus (vrsa), Gemini (mithuna), etc. When the mean anomaly of the Sun is between 0⁰ and 180°, the Sun is said to be in the six signs (or in the half-orbit) beginning with the anomalistic sign Aries; and when the mean anomaly of the Sun is between 90⁰ and 270°, the Sun is said to be in the six signs (or in the half-orbit) commencing with the anomalistic sign Cancer; and so on. The same is true also for the planets, Mars, etc. A rule relating to the Rsine of the Sun's mean anomaly: 2. (Of the parts of the Sun's mean anomaly lying) in the odd quadrants, calculate the Rsine; and (of the parts lying) in the even quadrants, calculate the Rversed-sine. The method ¹ This rule occurs also in SuSi, ii. 29; Br.Sp.Si, ii. 12(i); ŚiDVy, I, ii. 10; Sise, iii. 12; Siśi, I, ii. 18-19(i). 2 Or, that the mean anomaly is in the six signs (or in the half-orbit) beginning with the sign Aries.
