The Astronomical Observatories of Jai Singh c15.s1.t2.1

c15.s1.t2.1

66. (a) The Jyotisha Vedāṅga¹ and the Sūryaprajñapti contain the earliest formal astronomical statements. The former introduces the 5-year cycle of 1830 apparent solar days. The year was tropical in theory and contained 366 apparent solar days, and was, therefore, too long. The sidereal year was 367 sidereal days. The lunar day or tithi was 61/62 of an ordinary day, but was reckoned as equivalent to an ordinary day for calendar purposes, one tithi being omitted as occasion required. There were 27 nakshatras, each supposed to occupy 360/27 = 13 1/3 degrees of the ecliptic, and each nakshatra was considered to be divided into 124 equal divisions, or aṃśas. The sun, therefore, traversed 5 × 27 asterisms in the five-year cycle, or 5 × 27 × 124 / 1830 aṃśas a day; and to traverse one nakshatra it took 13 1/3 days = 13 days 335 kalās, since there are 603 kalās in one day. The moon traversed 67 × 27 / 1830 = 603/610 nakshatras in one day, and one nakshatra in 1 day 7 kalās.