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

35 by dividing the product of the number of lunations in a Kalpa and (12 x + y) 30 + t where x is the number of elapsed years, y the number of elapsed lunations t the number of elapsed tithis in the current lunar month at the time when the Ahargaṇa is being computed and S the number of Solar days in a Kalpa. The form of the Avama-Sesha was formerly stated as R / T. The procedure given is as follows. In the first place, we are asked to assume that the number of elapsed solar days is equal to the number of elapsed tithis from the beginning of Chaitra ie the beginning of the luni-Solar year, since we do not know when the Solar year began; so, at the rate of 1° per a Solar day (A Solar day is not a mean solar day, Vide definition given before under verse 8. Bhagaṇādh- yāya) the Sun’s position is given by as many degrees as there are elapsed tithis; and the Moon’s position must be 13 times the same since each tithi means an increase of 12° in the elougation and if x° be the Sun’s position, the Moon’s position must be 12 x° ahead of the Sun ie 13 x°. Having got thus approximate positions of the Sun and the Moon, we have to make amends for the roughness of the assumption made. In assuming that the longitude of the Sun is equal to the number of elapsed tithis, we have over- estimated the longitude since it has to begin from the beginning of the solar year. The time in between the beginnings of the luni-Solar year and the solar year is known as the Adhimāsa-Sesha at the time of the beginning of the solar year, measured in tithis; also, we have com- mitted an error in assuming the Sun’s rate to be 1° per tithi. This also is due to Adhimāsa-Sesha subsequent to the beginning of the Solar year upto the day concerned- Thus the entire error committed by assuming the Sun’s longitude to be as many degrees as there are elapsed tithis from the beginning of the luni-Solar year. is no other than the Adhi- māsa-Sesha at the day concerned, But this Adhimāsa- Sesha is of the form (R′ × 30) / S as mentioned and is in tithis.