सिद्धान्तशिरोमणि: गणिताध्याय (भास्कराचार्य - ग्रहगणित, मध्यमाधिकार व स्पष्टाधिकार सटीक)

536 process till an invariable quantity is obtained in ghatis. This is the time by which the moment of the pāta has elapsed or after which it is going to occur. Comm. (1) It might be asked “why bother finding the declinations at all, when it is defined that Vyatīpāta happens when the sum of the longitudes of the Sun and the Moon is equal to 180° and Vaidhṛti is defined when the sum is equal to 360, since easily we could know when this happens without taking recourse to declinations?” The problem is not that simple. The above definition in terms of the sum of the longitudes is an approximate statement, because, the original and correct definition is that their declinations must be equal in magnitude. If they be equal in magnitude but opposite in direction, they constitute Vaidhṛti Yoga. If they be both equal in magnitude and direction, the situation constitutes Vyatī- pātayoga. In other words, when the diurnal paths of the Sun and the Moon coincide, the moment will be Vyatīpāta. If on the other hand their diurnal paths are of equal dimentions but one to the north of the celestial equator and the other to the south, then the moment is Vaidhṛti. Though the sum of the longitudes happens to be 180°, the diurnal paths may not coincide because the Moon does not actually move on the ecliptic. So the situation is more complicated. Further the calculation of the declination of the Moon is to be done by calculating the Asphuṭakrānti ie. the declination of the point of the ecliptic which indicates the longitudinal position of the Moon and his celestial latitude ie. the Asphuṭavikṣepa from the known position of the Node, and then by rectifying the Asphuṭavikṣepa to obtain the Sphuṭavikṣepa and then adding the Asphuṭa- krānti to the Sphuṭavikṣepa to obtain the Sphuṭakrānti. (2) The latter half of verse (11) and the first half of verse (12).