A History of the Kerala School of Hindu Astronomy (in Perspective) c7.s7.20

c7.s7.20

Haridatta based his system on the *Āryabhaṭīya*, but improved upon it in several ways. He made computation easier by specifying simple multipliers and divisors for the various calculations, including the derivation of the positions of the planets. His use of the *Kaṭapayādi* notation made his composition elegant. He introduced the unique system of enunciating graded tables of the Sines of the arcs of Anamoly and of Commutation of the different planets (*Manda-jyā* and *Śīghra-jyā*) at intervals of 3° 45’, to facilitate the computation of the true positions of the planets. His *Grahacāra-nibandhana* being only the computation manual of the system, deals, mainly, with the calculation of the Kali days elapsed, *tithi* and *nakṣatra* of any day, the mean and retrograde motion of the planets and their Mean and True positions. One of the corrections introduced by Haridatta to make Āryabhaṭan results more accurate, is called *Bhaṭa-saṃskāra* or *Śakābda-saṃskāra* (on account of its being calculated for the years beginning from the ‘*śakābda*’ of Āryabhaṭa, viz., 444), and is particularly significant. This correction specifies that for every completed year after Śaka 444, a correction in minutes (*kalā*) of −9/85, −65/134, −13/32, +45/235, +420/235, −47/235, −153/235 and +20/235 should be made to the Mean positions of the Moon, Moon’s apsis, Moon’s node, Mars, Mercury, Jupiter, Venus and Saturn, respectively, no correction being necessary in the case of the Sun.¹