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

480
Verses 11 and 12. If the Prāk-Dṛk-graha has a
longitude greater than that of the Sun or the Paschima-
Dṛk-graha has one less than that of the Sun, the sum of
the prescribed Kālāṁśas and Iṣṭa-Kālāṁśas converted into
minutes of arc will have to be used to compute the elapsed
days or the days after which the respective phenomenon is
going to occur.
If the Iṣṭa-Kālāṁśas y be greater than the prescribed
namely x, the reverse to what has been stated in the second
half of verse (8) and in the first line of verse (9) happens
ie. a phenomenon which has elapsed when y < x will happen
in the future and vice versa.
Comm. If the Prāk-Dṛk-graha has a longitude greater
than that of the Sun, (since the prescribed Kālāṁśas are
between the planet and the Sun, the planet being behind
the Sun, and the Iṣṭa-Kālāṁśas are now on the other side
of the Sun) the planet has advanced over its position of
heliacal setting be it a superior planet or inferior by the
sum of the prescribed Kālāṁśas and Iṣṭa-Kālāṁśas. Hence
the days that have elapsed after the heliacal setting have
to be calculated with the sum of the two Kālāṁśas. If it
be also a case of a retrograde inferior Prāk-Dṛk-graha
rising, having a longitude greater than that of the Sun,
even then the prescribed Kālāṁśas are behind the Sun and
the Iṣṭa-Kālāṁśas ahead of the Sun. So from the position
of the planet’s heliacal rising, the Sun and the planet have
advanced in opposite direction to a distance which is the
sum of the prescribed Kālāṁśas and Iṣṭa-Kālāṁśas. Hence
computation has to proceed with the sum of the two
Kālāṁśas to get the time that has elapsed after the planet’s
heliacal rising. Similar is the argument for the Paśchima-
Dṛk-graha.
We have commented on verses from the latter half of
(8) upto (10) where the Iṣṭa-Kālāṁśas y happen to be less