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

519 Verses 17 to 21. Ancient astronomers happened to give a list of polar longitudes and polar latitudes at a time when there were no Ayanāṁsas ie. when the zero-point of the ecliptic as taken by the Hindu Astronomers namely Aświnī coincided with the modern zero-point namely r. In fact these polar longitudes and latitudes do change if there be Ayanāṁsas. Here in this case from the polar latitudes the celestial latitudes are to be computed in a reverse process; with the half of these celestial latitudes, the Āyana-Dṛk-Karma is to be effected in the reverse process to obtain the celestial longitudes. After having obtained the correct celestial longitudes and celestial latitudes, now, bringing the Ayanāṁsas into the picture, compute the correct Dṛk-Karma and also rectify the celestial longitudes, to obtain the correct polar longitudes and polar latitudes to compute the moment of polar latitudinal conjunction. This case may be taken when the Ayanāṁsas are large, otherwise, a small difference there will be, (which does not matter). Comm. Bhāskara·gives the process in the course of the commentary. We have the formula Asphuṭa Vikṣepa × Yaṣṭi Sphuṭa Vikṣepa = ——————————————————————— Radius Here we know Sphuṭa Vikṣepa. At once, we could not Sphuṭa Vikṣepa × Radius say Asphuṭa Vikṣepa = ——————————————————————— Yaṣṭi computing Yaṣṭi from the modern Ayanāṁsas. Yaṣṭi is a function of declination too, because the Āyanavalana is a function of declination. We know, the declinations change in the wake of precession of the equinoxes. So, there is no point in taking the value of the present Yaṣṭi. We should compute it for the Āyanaśūnyakāla or for the time when Aświnī coincided with r. Then the formula could be applied. Then with this celestial latitude obtained, Āyana-Dṛk-Karma is to be effected to obtain the present