A History of the Kerala School of Hindu Astronomy (in Perspective) c9.s5.5

c9.s5.5

Computation of the positions of the Sun and the Moon from the Shadow (Chaya) caused by them and vice versa had practical utility in the social and religious life of the people of mediaeval times. Besides calculations made on the basis of the Śaṅku (gnomon), intrinsic calculations involving the Mahācchāyā (Great Shadow or Sine Zenith distance) and the Mahāśaṅku (Great gnomon or Sine Altitude) had been developed in this behalf. Some of the Pañcabodhas and other karaṇa texts mentioned above have sections devoted to Shadow computation. Besides these, several independent works devoted solely to this subject have also been produced. Among the works of this category may be mentioned five different works, all entitled Candracchāyā-gaṇita, one of these being by Parameśvara, another by Nilakaṇṭha Somayāji and the others anonymous; two of these works have also commentaries. Other works on the subject include the Chāyāgaṇita, Chāyāgraha-gaṇita, Chāyādigaṇita and two different works having the common title Sūryacchāyādi-gaṇita. Acyuta Piṣāraṭi, too, has written a succinct work on the subject, entitled Chāyāṣṭakam.