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JANUARY, 1987
in measuring shadow-lengths to such an extent that summer solstice had been determined up to 30 muhurtas of one day.13
4. Kinematics of the Sun and the Moon
Jainas had determined the spiral paths of the solar and the lunar motions whose equations are akin to that of the Archimedian spiral. Such a kinematical model owes its provenance to the concept of a solar or lunar maṇḍala (diurnal circle) which implied a notion of declination.14 The notion of declination has neither been found in Vedānga Jyotişa nor in Pauranic or Buddhistic texts so far. Later the phenomenon of heliacal combustion of Venus had also been studied15.
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5. Jaina Calendar
Jainas had strived for the reformation of the quinquennial cycle of Vedänga Jyotişa and the beginning of the five year cycle had shifted from Winter solstice in Vedänga Jyotisa to Summer solstice in Jaina astronomical system. Jainas had classified nakṣatras into kula (category), upakula (sub-category) and kulopakula (sub-sub-category) nakṣatras depending upon their positions with respect to moon's position among asterisms at syzygies. Thus, the five-year cycle of sixty-two lunar months was fixed on the sidereal lunar zodiac. It is worthy of note that the theory of classification of nakşatras into kula, upakula and kulopakula does not fit exactly in the theory of Jaina five year fixed calendar based on mean motion of the moon. It seems plausible that the five-year fixed calendar was used for regulating their religious life whereas the concept of classification of nakṣatras into kula etc. was devised to study lunar motion for astronomical purposes. Such a classification of nakşatras has not hitherto been found anywhere else.16
6. Cycles of Eclipses
Jainas had found out a unique cycle of eclipses depending upon two component cycles, viz. forty-two eclipse months cycle of lunar eclipses
13 Lishk, S. S. (1983), "Post-Vedanga Pre-Siddhantic Indian Astronomy", Jain Journal Vol. 17 No. 3, pp 88-95.
14 Lishk, S. S. (1984), "Notion of Declination Implied in the Concept of Mandala (Diurnal Circle) in Jaina School of Astronomy", Jain Journal, Vol. 18 No. 3, pp. 83-101.
15 Lishk, S. S. (1983), "Kinematics of Venus in Bhadrabahu Samhita", Jain Journal, Vol. 18 No. 1, pp. 1-19.
16 Lishk, S. S. (1980), "A Note on Jaina Calendar", The Jaina Antiquary, Vol. 33 No. 2, pp. 15-77.
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