MEAN LONGITUDE OF A PLANET That is to say mean longitude of the desired planet in minutes (mean longitude of the known planet in revolutions, etc., reduced to minutes) x (revolution-number of the desired planet) revolution-number of the known planet This rule and the previous one are based on the following principle. If there are two planets P and g, then revolution-number of P: revolution-number of g
- (mean longitude of Pin revolutions etc.) : (mean longitude of g in
revolutions etc.). Alternative rules for deriving the mean longitude of the Moon from that of the Sun and vice vers: Il. Or, multiply the chargeta by the number of intercalary months in a ५ge am divide (the product) by the number of civil days (in a yugg) : bhe result is in terms of revolutions, etc. Add that to tbhirteen times the mean longitude of the Sun. (This is the process) to obtain the mean longitude of the Moon. 12. Or, subtract the result obtained (in revolutions etc.) from the mean longitude of the Moon and take one-thirteenth of the remainder : this is stated to be the mean longitude of the Sun by the mathematicians whose intellect has been awakened by the grace of the teacher. The following is the rationale : We know that intercalary months in a yuga = lunar months in a yuga – solar months in a yuga. But lunar months in a yuga = Moon's revolution-number – Sun's revolution-number; and solar months in a yuga = 12 (Sun's revolution number). • This rule is found also in BrspS, xi. 33; iDV१, , i. 24 (i)Sise ii. 19.