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

507 It is to be noted that these longitudes are the same given by Brahmagupta originally and copied by S'rīpati as well as the corrections indicated above. But herein a mistake was committed as clarified by Bhāskara later in the end of the chapter namely that the polar longitudes are subject to what is called Āyanavikāra though the celestial longitudes are not. We say that the celestial longitudes are not subject to such an Āyanavikāra ie. that change due to the phenomenon known as the precession of equinoxes, because the Hindu system is Nirayana ie. reckons the longitudes from the first point of Aswinī which is its zero point instead of reckoning from r. If longitudes are measured from r, as r is preceeding, the longitudes of stars will be steadily increasing all at the same annual rate of precession namely about 50-25" per year. These increasing longitudes of the modern system go by the name Sāyana longitudes. It might be thought that since the polar longitudes also are measured from Aswinī and along the ecliptic like celestial longitudes, they also don't vary like the Nirayana celestial longitudes ; but it is not so, because the effect of precession on the right ascension and declination of a star have both their effect upon the polar longitude as well as polar latitude. We cannot say that Bhāskara did not know this but we may say that the effect on the polar longitude and latitudes were construed by him as neglible and would be appreciable only in the long run. Verses 4, 5, 6. Sphutas'aras or rectified latitudes of the stars. Aswinī 10°- 0 north Ārdrā 11 - 0 south Bharaṇī 12°- 0 ,, Punarvasū 6 - 0 north Kṛtticā 4 -30 ,, Puṣyamī 0 - 0 ,, Rohinī 4 -30 south Asreṣā 7 - 0 south Mṛgas'irṣa 10 - 0 ,, Makhā 0 - 0 north