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

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the period of diurnal rotation of the earth is of constant
magnitude. In the data given above, the time is normally
given in Sāvana units, ie. mean solar units. A Sāvana
day is of 60 × 60 × 6 + 59 asus, which is greater than a
sidereal day by 59 asus because the mean Sun advance by
59' — 8'' per day among stars and as such the Sun-rise the
next day is belated by 59 asus approximately. The given
time in Sāvana units could be converted into sidereal
units as per the approximate ratio 21600 : 21660 which
means for every Sāvana nādi we have to add one asu or
for every hour four seconds. Then the procedure of finding
the Lagna will be a little different from what it would
be if we proceed with the Sāvana units. The complex-
ity mentioned before, arises out of the Sāvana units,
and this has been explained by Bhāskara in Golādhyāya
under the title तात्कालिकीकरणवासना in the beginning of the
chapter called त्रिप्रश्नवासना. Now the procedure will be
explained. Let (Fig. 30) S' be the position of the Sun
at the Sun-rise and S his position at the time at which
the Lagna is to be found so thst the Sun has advanced
by S'S ie. which measured in minutes of arc is called gati-
kalās. In a mean solar day these gatis-kalas would be 59,
and in the given time after Sun-rise they will be
proportional. The time given after Sun-rise pertains
to the rising time of the arc S'L which we have in sidereal
units. We shall first find the Lagna using sidereal units
by measuring S'L, so that we may latter understand
Bhāskara's reasoning for his stipulation of तात्कालिकीकरण
on which basis he finds the Lagna with the Sāvana units
taking the position of the Sun at S instead of S'.
We know the position of the sun at sun-rise ie. S', so
that the rising time of As' ie. the previous arc in the Rāsi
in which the Sun is situated is given by Bhuktasus defined
above and the rising time of S'B the remaining arc
of the Rāsi is given by Bhogyāsus. Subtract from the
given time converted into sidereal units if they are not