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

LUNAR ECLIPSES Verse 1. The ritualistic purpose served at the time of an eclipse. Scholars of Smṛtis and pūrāṇas declare that prayer, charity or offerings to gods made in fire at the moment of an eclipse conduce to much spirituality. Hence I give hereunder the methods of computing the moment of an eclipse (lunar or solar) in as much as such a knowledge apart from its religious importance, is also wrought with a beautiful mathematical treatment. Verse 2. The initial procedure to be adopted to compute an eclipse. To know the occurence of a solar eclipse, find the exact moment of the New Moon, which is indicated by the equality of longitudes of the Sun and the Moon, and to know the occurence of a lunar eclipse compute the exact moment of the full Moon which is indicated by the fact that M = S + 180° where M and S are the longitudes of the Moon and the Sun, agreeing in degrees, minutes and seconds, though differing in Rasis by six. Also compute the longitude of the Node (Rāhu) for the moment as directed. Comm. Having ascertained the possibility for the occurence of a solar eclipse, we are directed to compute the positions of the Sun, the Moon and Rāhu for the day of the New Moon. The Sun and the Moon are to be rectified for corrections like Desāntara, Bhujāntara, Udayāntara etc. From the elongation of the Moon the tithi is to be computed and the method of successive approximations called Chālana Karma is to be used to obtain the exact moment of conjunction. This process of