Aryabhata

Aryabhata is the author of several books on mathematics and astronomy, some of which are lost.
His major work, ''Aryabhatiya'', a compendium of mathematics and astronomy, was extensively referred to in the Indian mathematical literature and has survived to modern times. The mathematical part of the ''Aryabhatiya'' covers arithmetic, algebra, plane trigonometry, and spherical trigonometry. It also contains continued fractions !!! , quadratic equations, sums-of-power series, and a table of sines( part of syllabus in CED ).

The ''Arya-siddhanta'', a lost work on astronomical computations, is known through the writings of Aryabhata's contemporary, Varahamihira, and later mathematicians and commentators, including Brahmagupta and Bhaskara I.  This work appears to be based on the older Surya Siddhanta and uses the midnight-day reckoning, as opposed to sunrise in ''Aryabhatiya''. It also contained a description of several astronomical instruments: the gnomon (''shanku-yantra''), a shadow instrument (''chhAyA-yantra''), possibly angle-measuring devices, semicircular and circular (''dhanur-yantra'' / ''chakra-yantra''), a cylindrical stick ''yasti-yantra'', an umbrella-shaped device called the ''chhatra-yantra'', and water clocks of at least two types, bow-shaped and cylindrical.

A third text, which may have survived in the Arabic language translation, is ''Al ntf'' or ''Al-nanf''. It claims that it is a translation by Aryabhata, but the Sanskrit name of this work is not known.
Probably dating from the 9th century, it is mentioned by the Persian scholar and chronicler of India, Abū Rayhān al-Bīrūnī.

Astronomy and Religion

In India astronomy and religion was interelated even during the early times, beginning from the Vedic Period when the Vedas were composed.Sarma veda notes that the Vedas are compositions of religion, and not science.However, they  hold a enormous amount of astronomical information.The religious texts of India often contained astronomical observation for carrying out ritual associated with religion at a certain time.

Hindus kept a panchangam or calculations of ''tithi'' (lunar day), vara (weekday), nakshatram, and ''karan'' (half lunar day) for social and religious events.Klostermaier states that: "Indian astronomers calculated the duration of one ''Kalpa'' (a cycle of the universe during which all the heavenly bodies return to their original positions) to be 4,320,000,000 years.

This can be significantly noted in HINDU RITUALS when the mantras are recited , the exact position and time of occurrence of the ritual is mentioned.

What did they do ?

Astronomy in india was part of religion and culture.Ancient India's contributions in the field of astronomy are well known and well documented. The earliest references to astronomy are found in the Rig Veda, which are dated 2000 BC. By 500 AD, ancient Indian astronomy has emerged as an important part of Indian studies and its affect is also seen in several areas of that period. Apart from this linkage of astronomy with astrology in ancient India, science of astronomy continued to develop independently, and culminated into original findings like determining eclipses, horoscopes, and so much more.

Ancient Indian astronomy was so advanced that it even predicted the presence of black holes !!!

checkout the following link to have a look at an Ancient Indian Observatory http://www.youtube.com/watch?v=pcQk4JE2Xbg