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There were two Ayans in a year namely Uttarāyana and Daksināyaņa marking the period of northward and southward motion of the sun. A Vishwa day (an equinoxal day) is mentioned between the two ayanas. A yuga is also mentioned, but it is meant only for a period of five years in the vedic period. Within the belt along which the Moon moves around the path of the Sun (ecliptic), where in its maximum celestial longitude is five degrees north or south, a Nakşatra system was supposed to consist of 27 Nakșatras, all of which were named in vedic times were slightly different from their present names. Among the planets, Brahspati (Jupiter), Sukra (Venus) and Rāhu are mentioned, but it is not easy to see how those who constantly watched the Naksatras, could have left the other planets unnoticed. Comets and meteors (Dhumketa and Ulkās) are clearly mentioned. There is no mention of a seven days week of zodiac signs (rāśis in the Vedas.
(iii) Vedāmga Jyotisa pariod of astronomy -
For every Veda, rules were given for calculating astronomical results in a text called Vedānga Jyotişa supposed to be written by the unknown writer Leghadha. The period might be about the thirteenth century B.C. A period of five years was called yuga and the names of the five years were Samavastara, Parivastara, Idavastara, Anuvastara and Idvastara. A solar year was supposed to consist of 366 days. A yuga was supposed to consist of 1830 civil days, sixty two (synodic) months of moon, thirty omitted tithis, two intercalary months and five mean remolutions of the sun. Vedāmga Jyotișa dealt only with rough calculations of solar and lunar elements. There were no calulations for planets.
(iv) Mahābhārata period of astronomy -
During this period, Indian had knowledge of 5 planets; they observed them in the framework of Nakşatras belt and in conjunction with one another. They knew about the retrograde motions of planets and they attached astrological significanse to all these phenomena. They had a time scale of kalpayuga of 4.32x109 years and of a Mahāyuga of 4.32x106 years consisting of Kalayuga of 432000 years. Dvāpara yuga of 864000 years. Tretāyuga of 1296000 years and satayuga of 1728000 years.
Siddhānta Jyotişa period of India astronomy : Siddhānta Jyotişa means a system which gives rules for calculating time, motions of planets etc., from the beginnings of the universe (Sreshtiādi) to the end (pralya). A book is called Karana if it gives rules for calculating astronomical events from a fixed epoch, other than the beginning of yuga of Kalpa. The period in which these books were written is called the Siddhāntica Jyotişa period.
31644, 23 (3), 2011
