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

520 polar longitude, using the modern Ayanāṁsas. Since in this process, we have no definite knowledge of the then celestial longitude ie. of the Āyanasūnyakāla, the method of successive approximation is appealed to. But this method of Bhāskara may be modified to an easier pro- cess as follows. Let rL, LS be the polar longitude and polar lati- tude of a star as given by Acharyas in whose time the Hindu first point of the zodiac coincided with r. It is required to find rN and NS the celestial longitude and latitude which hold good even today becaus rN and NS are the same as AN, AS, A being the first point of Aświni and a celestial longitude measured from A along the ecliptic is not subject to change on account of precession of the equinoxes as well as the celestial lati- tude. From the spherical triangle rLM, cot rLM = cos rL tan ω (1) and from the triangle SNL, tan LN = cos SL̂N × tan SL = cos rLM tan SL (4) and sin SN = sin SL × sin SLN = sin SL × sin rLM (5). From (1) the angle rL̂M is obtained ; substituting this value in (2) and (3) LN and SN are obtained. Adding LN to rL we have rN. Thus the celestial longitude and latitude are found far more easily and more accurately than from the laborious method indicated which gives only approximate results. Here ends the Bhagrahayutyadhikāra.