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

226 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