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

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planet at the moment are to be computed. The time in
between the two lagnas, which will be in Sāvana measure
pertaining to the planet gives the time that has elapsed
after the rise of the planet.
Comm. According to computation, the difference of
times of the current lagna and the Udayalagna as com-
puted taking the present position of the planet will be the
time measured along the diurnal path of the planet and as
such is in Sānava measure.
Bhāskara mentions here a very subtle point. In the
analysis the latitude of the planet is taken into account
while finding the Udayalagna. Time measured in this
case is called Kṣetrātmika and not Kālātmika for the
following reason. Suppose A is the Udayalagna of the
planet and B the current lagna both points being on the
ecliptic. Let us say that the current lagna is posterior to
the Udayalagna (there is no loss of generality in supposing
this). By the time of the current lagna, the planet is no
more at A but will have moved a little towards B. Let the
present position of the planet on the ecliptic be A'. The
corresponding arc of AB on the equator gives the sidereal
measure of the time that has elapsed after the rise of the
planet whereas the corresponding arc of A'B on the
equator gives the Sāvana measure of the same time. Here
this Sāvana is that pertaining to the planet and not that
pertaining to the Sun which is Saura Sāvana. In other
words it is the Sāvana pertaining to the particular planet,
because the arc AA' is traversed by the planet in question
as per its own velocity.
The stress is here on the word Tat-Kāla-graha, ie.
the longitude of the planet at the moment at which the
shadow or the zenith-distance of the planet is sought.
Taking this as the position of the planet and taking the
latitude of the planet also into account compute the
Udayalagna. This will be A' cited above. To obtain the