ब्राह्मस्फुटसिद्धान्त (ब्रह्मगुप्त - शून्य, कुट्टक, बीजगणित एवं सम्पूर्ण २१ अध्याय सान्वय सटीक)

CHAPTER VI Indian Luni– Solar Astronomy In this chapter, it is proposed to give an account of astrono- mical constants and the equations in Indian luni-solar astronomy and to present a comparative view of these quantities with the corresponding ones in Greek and modern Astronomy. This acco- unt has been reproduced from P. C. Sengupta's. Appendix I of the Khaṇḍakhādyaka It has been shown that in many cases the Indian values of these constants are more accurate than the Greek values. and in Indian lunar astronomy the equations or inequalities discovered are the most startling. Solar Astronomy In solar astronomy the length of the year was determined by Āryabhaṭa¹ from the heliacal risings of some bright star at the intervals of 365 and 366 days. (1) The year according to the Āryabhaṭīya = 1577917500 / 4320000 days = 365.2586805 days, = 365 da. 6 hrs. 12 mins. 29.64 secs. (2) The same = 1577917800 / 4320000 days = 365.25875 days. = 365 da. 6 hrs. 12 mins. 36 secs., according to the Khaṇḍakhādyaka, the Sūryasiddhānta of Varāha and the modern Sūryasiddhānta. (3) It is = 1577916450 / 4320000 days = 365.2584375 days, = 365 da. 6 hrs. 12 mins. 9 secs., according to the

1, P. C. Sengupta, "Aryabhata's Method of determining the Mean Motions of Planets," Bulletin of the Calcutta Mathematical Society. Vol. XII, No. 3.