Jyotihshastra: Astral and Mathematical Literature c4.s4.62

c4.s4.62

A second category of koṣṭhakas that were popular in India provides tables for computing the beginnings (and ends) of tithis (periods during which the elongation of the Moon from the Sun increases by 12°), nakṣatras (periods during which the longitude of the Moon increases by 13; 20°), and yogas (periods during which the combined motion of the Sun and the Moon equals 13; 20°). The computations of the true instances of the beginnings of tithis and yogas is made complex by the fact that both of the luminaries have varying velocities, the Sun's dependent on the distance of its mean longitude from a more or less fixed sidereal point (its mandocca) and the Moon's on the distance of its mean longitude from a constantly moving point (its mandocca). The solutions adopted by various Indian koṣṭhakakāras are not yet understood in their totality by the present writer. The tithis, nakṣatras, and yogas themselves needed to be tabulated for the convenience of astrologers computing muhūrtas and of the constructors of pañcāṅgas which informed the populace of the details of the calendar and the proper times for festivals and the performance of saṃskāras.