Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v1.c6.s2.5

v1.c6.s2.5

Saṃhitā and Jātaka, the two branches of astronomy, depend upon the motions of planets and stars. The chief aim of our astronomy is the prediction of actual planetary positions, that is foretelling what place in the sky a particular planet would be occupying at a particular time. Its complicatedness is inherent. An accurate knowledge of the mean motions and positions of planets emanates from an accurate knowledge of their true positions and motions. Even before they acquired the capacity to predict accurately their apparent positions, the ancients did possess a tolerably accurate knowledge of planets’ mean motions and positions. This was the preliminary stage. The Siddhāntas and other available astronomical works deal with the calculations of true positions and motions of planets. A considerable period of time must, however, have elapsed before man’s knowledge of astronomy reached that stage.