28 MEAN LONGITUDE OF A PLANET A rule for finding the mean longitude of Jupiter : 39. Multiply the grahadeha by 22 and divide by 375: these are minutes, etc. Add them to one-twelfth of the Sun's (mean) longitude (in revolutions, etc.) : the result is the (mean) longitude of Jupiter.¹ The mean motion of Jupiter per solar day 364224 4320000 Hence the rule. - = of a degree 1/12 of a degree +22/375 of a minute. Corrections to be applied to the mean longitudes of the Moon's apogee and ascending node, and to the ahargana: 40. Add three signs to the mean longitude of the Moon's apogee. Subtract the (mean) longitude of the Moon's ascending node from 12 signs and then add 6 signs. Also (if necessary) add one to the ahargana obtained by proportion (in stanza 7 above). So say the astronomers whose hearts are devoted to Aryabhaṭa's system of astronomy (bhatasastra). At the beginning of Kaliyuga, according to Aryabhata I's system of astronomy, the mean longitude of the Moon's apogee was 3 signs and that of the Moon's ascending node. 6 signs. Hence the addition of 3 signs to the mean longitude of the Moon's apogee and of 6 signs to the mean longitude of 'the Moon's ascending node prescribed by the author. The longitude of the Moon's ascending node has to be subtracted from 12 signs, because the motion of the Moon's ascending node is retrograde. The remaining chapter deals with the solution of pulverisers (kuṭṭākāra) having reference to problems in astronomy. ¹ Similar rules occur in BrSp.Si, xxx. 35 and SiDVṛ, I, i. 51 (i).
