INDIAN LUNI-SOLAR ASTRONOMY the truth or fallacy of the supposition." We next consider the second inequality of the Moon. 114 Moon's Second Inequality or Equation In ancient times it was Prolemy who first really found a second inequality of the Moon. According to Godfray (Lunar Theory, p. 107) "by dint of careful comparison of observations he (Ptolemy) found that the value of this second inequality in quadrature was always proportional to that of the first in the same place, and was additive or subtractive according as the first was so; and thus, when the first inequality was at its maximum or 5°1', the second increased it to 7° 40' which was the case when the apse line happened to be in syzygy at the same time." It is well known that though Ptolemy discovered the second inequality in the Moon's motion he was not able to ascertain its true nature. His corrections in this case are true when at the quadrature the Moon's apse line passes through the Sun or it is at right angles to the line joining the Earth and the Sun In the general case his construction does not lead to the elegant form of the evection term as we know it now, nor does it lead to the nice form in which it was given by later Indian astrono- mers from the time of Manjula (or Muñjala, 854 Saka era-932 A.D.). As has already been pointed out, the early Indian astrono- mers from Aryabhata to Brahmagupta aimed at accuracy in lunar calculation only for the eclipses and syzygies, and did not interest themselves about the Moon's longitude at the quadra- tures. Hence this second inequality is absent in the works of these makers of Indian astronomy, as also in the Pre-Ptolemaic Greek astronomy. This points to the conclusion that in both the earlier Indian and Greek systems of astronomy, the modes of observation of the Moon were copied from an earlier system of astronomy whether Babylonian or Chaldean. Even in the Romaka Siddhanta of the Pancasiddhantika, there is no mention of evection. Thus inspite of the transmission of a vague system of Greek astronomy, Indian astronomy as developed by Arya- bhata and Brahmagupta must be regarded as independent and 1, Godfray's Lunar Theory. pp. 108-110. 2. Vide the Summary in P.C. Sengupta's paper, "Aryabbeta the Father of Indian Epicyclic Astronomy." Journal of the Department of letters, vol. XVIII, Calcutta University Press.
