In India people had started the use of the astronomical instruments before 1000 BC. During this period one of the prominent books ‘Suryasidhanta’ was written for astronomical calculations.
Please note that there are several works with the same name, BUT the Original writer of Surya Siddhanta is UNKNOWN.
The title ‘Suryasidhanta’ means sun theory and it highlights the calculations of positions of stars and planets. Some of the Indian mathematicians later have developed their own instruments and developed their own methods to facilitate the theory of ‘Suryasidhanta’. Introduction of zero in mathematics and the decimal method of calculation is one of such invaluable contribution. We should note that Varahamihira had contrasted Surya Siddhanta along with his 4 other treatises in the panchsiddhantika viz. Paitamaha Siddhantas, Paulisha , Romaka Siddhantas and Vasishta Siddhanta. Citation of the Surya Siddhanta is also found in the works of Aryabhata.