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

208 gaṇa found by us is what is called Madhyama Sāvana- ahargaṇa or number of days according to mean solar reckoning, a reckoning made on the basis of taking uniform motion of the Sun in right ascension. The planets computed for the Sun-rise on this basis, are to be corrected for the true Sun-rise which goes according to the measure of ☉ ie. the true longitude of the Sun. But in the name of Bhujāntara we have-effected the correction for ☉ - l ; so what remains is to effect correction for l - a. This correction is known as Udayāntara. In other words, since we could not compute the Sphuṭa Sāvana-ahargaṇa, when we deem that x days have elapsed according to the mean solar reckoning from, the epoch upto the mean Sun-rise x ± f might have elapsed according to Sphuṭa Sāvana-ahargaṇa where f is a fraction. A correction is to be effected for this fraction f of a day and it is of the form ☉ - a = ☉ - l + l - a. In the beginning Bhāskara said that mean planets are had being computed out of the mean solar ahargaṇa, at the time when the mean Sun is about the eastern horizon of the equator. Why did he say ‘about the horizon’? It is because the mean solar ahargaṇa indicates a Sun-rise on the basis of equal motion in right ascension whereas on the basis of equal motion in l, he would be about the horizon. Had we been able to compute Sphuṭa-Sāvana-ahargaṇa, we could have got direct the planetary position when the true Sun is on the horizon. The correction for the difference in ☉ and l having been attended to through Bhujāntara, we are now to attend to the correction for the difference l - a. Verse 64. Another way of looking at the same. Had we obtained the Ahargaṇa in terms of the local risings of the Rasis in the place of the equatorial, and computed the planetary positions for the local true Sun- rise obtained that way, we would have done the three