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modern times also, though mathematics has many users other than astronomers (and religion does not need mathematics very much now). Moreover, modern astronomy also depends on many other disciplines like physics, chemistry, biology etc. (which was not developed to the same extent as mathematics in ancient India).
2. Brief History of Ancient Indian Astronomy -
For convenience, this history is devided into two periods : (a) The PreSiddhāntica Period (b) The Siddhāntica Jyotişa Period.
The Pre-Siddhāntica Period is further divided into four parts. (i) Pre-Vedic Astronomy
Though there is no direct reference to astronomy in the antiquities found in the excavations of Mohañjo-dāro and Harappā, yet it is believed that a civilization so highly developed could not do without a calendar based on astronomy
(ii) Vedic period astronomy -
There are many astronomical references in the vedas, particularly the Yajurveda, which show that a system of astronomy, based on practical obsevations of moon and stars, existed for providing the calendar to enable the priests to perform yajñas, which had to be performed in different parts of the year and at different points of the day.
A day was reckoned from sunrise to sunset and the night was reckoned from sunset to sunrise. Each was divided into fifteen muhürats (48 minutes). The mūhūrats were named differently for each day and night of the dark and bright fortnights of a lunar month.
Besides these, there were three divisions of a day (pārvāhna, Madhyāhna and sāyahna) and five divisions of a day (prātah, Sanagava, Madhyamā, Aparahna and Säyahna) for rough division of time. The month used was the lunar month and all 30 days of the lunar months were given specific names. There were two groups of vedic people, one reckoned a month from full moon to full moon, and the other from new moon to new moon.
A year considered of twelve months (Madhu, Mādhava, Sukra, Sūchi, Nabhas, Nabhasya, Isha, Urja, Saha, Sahasya, Tapa and Tapasaya), spread over six seasons (Vasanta, Grisma, Varşa, Sarada, Hemanta and Sisira). Later, with the discovery of Nakşatras, the names of months were changed to their present names. Caitra, Vaišākha etc. The solar year was also started to be used along with the lunar month, and a thirteenth month Ahmaspati (intercalary) was introduced to regulate calculations.
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