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

472 in the course of half a sidereal day, these zenith-distances could not be equal, x and y cannot be equal. Second half of verse 2 and verse 3. To find the side- real time in between the given time and the time of the planet's rising. Find the time that has elapsed after the planet's rise, from a knowledge of the Iṣṭalagna at a given time and Prāk-Dṛk-graha ie. the longitude of the rising point of the ecliptic at the time when the planet rises. This time will be in Sāvana measure, because we have taken the planet's position at the given moment and not the position of the rising planet. From this time, know- ing the daily motion of the planet of the day in question, obtain the arc; that would have been traversed in between the moments. Subtracting this arc from the planet's position at the moment, the planet's position at rising would be obtained approximately; approximately, because as per the procedure enunciated in verse eleven, Graha- cchāyādhikāra, the Prāk-Dṛk-graha of the rising planet, and that obtained from the position of the planet at the moment differ. From this approximate time again com- pute the arc that would have been traversed by the planet during that time. Subtracting this arc which is nearer the truth from the planet's present position, we obtain a more approximate position of the rising planet. Again computing the Prāk-Dṛk-graha from this position, calcu- late the time from this Prāk-Dṛk-graha and the lagna of the moment. Repeating the process we will obtain the actual sidereal time in between the given time and the actual rising time of the planet. It is sidereal because, we have found the time as per the procedure of verse (11) referred to, where we have used तत्कालखेटोदय and not the actual ,खेटोदय, i.e the rising lagna of the planet obtained from the present position and not that of the rising planet.