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

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sidereal, we subtract the rising time of SA from the given
Sāvana time and the result will be the same, for,
— SA = — (S′A — S′S) = S′S — S′A. which means
subtracting SA from the time tantamounts to increasing
by S′S and subtracting S′A. This increase by S′S is add-
ing what have been defined as gati-kalas so that automati-
cally the Sāvana units got converted into sidereal units,
by taking the position S and subtracting SA instead of
taking the position S′ and subtracting S′A. The result is
the same. So, it is said ‘तात्कालिकार्कस्य’ in the beginning
of the verse 2.
In the second case mentioned in verse 4, if the time
given, falls short of the Bhogyāsus, then simply (x × 30) / T
where x is the time given in asus and T the rising time of
the Rāsi in which both the Sun and the lagna are then
situated gives the arc in degrees which if added to the
longitude of the Sun gives that of the lagna. Here also
the position ‘S’ counts.
Verses 5 to 6½. To find conversely the time that has
elapsed after Sun-rise given the lagna.
The Bhogyasus of the Sun and the Bhuktāsus of the
Lagna together with the rising times of intermediate
Rasis gives the time required.
If the Sun and the Lagna both be in the same Rāsi,
then the arc in between them, multiplied by T and divide
by 30, gives the time required.
If, however, the longitude of the Lagna falls short of
that of the Sun, ie. if the Sun be below the horizon, (in
this case SL > 180°) then finding the time of rising of SL
and subtracting from a day, we have the time of the Lagna
before Sun-rise.