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

437
First compute the time called Sthiti-khanda (as
mentioned in the chapter on lunar eclipses). The ending
moment of local Amāvāsyā or what is called the moment
of local conjunction is known as the Madhya-Grahakāla
or the moment of the middle of the eclipse. Subtract the
Sthiti-khanda from the computed time of Geocentric
conjunction ; the result will be the approximate Sparśa-
kāla. This has to be rectified for parallax in longitude
as well as the approximate Madhyagrahakāla of geocentric
conjunction to obtain the local Sparśakāla and the local
Madhyagrahakāla ; Similarly the Mokṣakāla, the Sammī-
lana and the Un-mīlanakālas are to be rectified for
parallax in longitude. But while effecting this correction
for the parallax in longitude, the Moon's latitude also
differs for the corrected time which in turn effects the
durations of Sthiti-khanda, Mokṣa-khanda etc. Correcting
the first computed Sthiti-khanda. Mokṣa-khanda etc. for
this variation in the latitude, and subtracting the Sthiti-
khanda from the time of Madhya-graha, we have a better
approximation for the Sparśakāla. In as much as parallax
in longitude, that in latitude, and the Moon's latitude vary
from time to time, and the times of Sparśa, Madhyagraha
etc. are effected by them, the process of computation
proceeds by the method of successive approximation.
Subtracting the rectified Marda-khanda from the rectified
Madhyagrahakāla, we have the true Sammīlanakāla ;
similarly adding the former to the latter we have the true
Un-mīlanakāla.
If, as mentioned before in verse 9, the parallax in
longitude is found without using the method of successive
approximation, the Sparśa-kāla and the Mokṣa-kāla are
had at once. But the latitude of the Moon and the parallax
in latitude are to be computed using the then longitudes
of the Moon and the non-agesimal.
Comm. Clear.