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

447 there is no parallax in latitude ie. no nati at all, as should be the case. Fig. 101 Fig. 102 Or, Bhāskara's argument could be better illustrated from figure 102. Let VS be the ecliptic where V is the Sun's Vitribha and S, the Sun. Let V'M be the Moon's orbit called Vikṣepamandala where V' is taken to be the Moon's Vitribha and M the Moon. Let S', M' be the deflected positions of the Sun and the Moon on account of parallax. ZV' = ZV + VV' = the arc of the Sun's Dṛk- kṣepa + the latitude at the point V called Vitribhalagna- Bāna, as formulated by Brahmagupta that ZV' is roughly equal to the Moon's Dṛk-kṣepa-Dhanus. (Strictly speaking ZV' ought to be perpendicular to the Moon's orbit V'M, if V' were to be the Vitribha of the Moon; but, as the latitude is small, the error is negligible). Let LS' and L'M' be the so-called Krānti-Sadṛśa-mandala and Vikṣepa Sadṛśamandala or parallel drawn to the ecliptic and the Moon's orbit through the deflected positions S' and M' of the Sun and the Moon. S'n is the Sun's parallax in latitude ie. Nati. Similarly Brahmagupta took M'n' to be the nati of the Moon as stated by Bhāskara. The error com- mitted will be therefore M'n'— S'n = (M'x' + x'n') — (S'x + xn) = M'x' — xn) cancelling x'n' and S'n which are roughly equal. Also xn could be roughly taken to be equal