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

473 This difference between the nature of the times was already dealt with. The matter of this verse appears to have been unnecessarily complicated by Bhāskara but on careful scrutiny it is not so ; for, the problem is to find the time that has elapsed after the rise of the planet upto a given time. Here the data are the given time and the corres- ponding position of the planet not on the horizon but elsewhere. We could not know immediately the time at which the planet rose. To find it alone, this method of successive approximation has to be used and there is no other go. Had we known the position of the planet while rising, the corresponding Prāk-Dṛk-graha could be found exactly and as this position of the Prāk-Dṛk-graha is a point of the ecliptic and the Iṣṭa-lagna ie. the rising point of the ecliptic at the given moment is also a point on the ecliptic, the time between the moments of rising of these two points of the ecliptic could be found in sidereal measure directly by noting the rising times of the Rāśis in between, without an appeal to the method of successive approximation. Verse 4. The computation of the times of heliacal rising and setting of a planet in contradistinction to its rising time during a day on account of earth’s diurnal rotation. The times of rising and setting of a planet have been dealt with. Now I shall tell the procedure to be adopted in computing the times of heliacal rising and setting of a planet. If a planet has a daily motion less than that of the Sun, it rises heliacally in the east, and sets in the west ; otherwise the reverse. Comm. Take the example of the superior planets, say that of Jupiter. Since Jupiter moves slower than the Sun, 60