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

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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).