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

225 longitude. Let rA, AB, BC, CD, DF be the successive Sāyana Rāśis called Sāyana Meṣa, Sāyana Vṛṣabha etc. (The Nirayana Rāśis also starting from the Hindu zero-point are called Nirayana Meṣa, Nirayana Vṛṣabha etc. and if in Hindu Astronomy we use the words simply as Meṣa, Vṛṣabha etc. especially in panch- āngas ie. the Hindu almanacs, we have to construe them as belong- ing to the Nirayana or the Hindu system whose zero-point is called Fig. 30 the first point of the constellation Aswini and not r). rL = rD + DL = an integral number of Rāśis, say, ‘n’ of them ie. n × 30° + DL, where DL is the arc of the Rāśi carrying the Lagna L. The question then resolves itself into knowing how many Rāśis precede ‘D’ from r and what the measure of DL is. The data are (1) the Nirayana longitude of the Sun as computed by the methods of Hindu astronomy (2) The Ayanamsa of the year ie. ‘ro’ where o is the Hindu zero-point of the ecliptic. (3) The time after Sun-rise at the place, given in Sāvana units at which we are required to find the Lagna. Finding the Lagna at a given point of time at a given place is not only necessary in astronomy but its importance is more in what is called horary astrology or Muhūrta Sāstra, whose purpose is to fix an auspicious moment for the performance of marriages etc. as well as in astrology in casting a horoscope. The finding of the rising times of the various Rāśis at the equator, as well as at a given place was dealt with in the previous chapter. Those rising times are found in sidereal units, a sidereal day being divided into 60 nādis, or 60 × 60 Vinādis or 60 × 60 × 6 asus. These units are of constant magnitude since a sidereal day, which is 29