[ 30 1 It is, however, in computing the moon's place that Chandra- sekhara has discovered some original corrections, -original in the sense of their having been unknown to the ancient astronomers of our country. It is curious to note that they failed to discover the perturbation, known as Evection which is said to have been detected by Hipparchus about 150 years B. C. It is an irregu- larity which may put the moon forward or backward over a degree. Paņạit Sudhákara Dvivedi informs us in his excellent manual, called Gapaka-tarangipi, that Muñjúla (A. D. 933) had something like "evection" in his karana named Laghumánasar He appears to have been the oldest Hindu astronomer who detected the irregularity, though curiously enough, his successors including Bháskara left it unnoticed. The next large irregularity of the moon, called "variation, has a period of one month, and a maximum of 39' 31". This inequality does not affect the time of an eclipse, and the fact sufficiently explains its absence in Sanskrit Siddhantas* It is said to have been detected by an Arabian astronomer, Aboul Wefa about the year 975 A.D., and ro-discovered by Tycho Brahe in the 16th century. The last large inequality of the moon's place is called "annual equation, and has the maximum amount of 11' 9. This was also discovered by Tycho Braho, It is singular that Chandras ekhara is the only Indian astro- nomer who has detected all the three important irregularities of From Driredi's Gapaka-tarahgini, it appears that Nityananda in 2639 A, D, uued a correction called Pakshika. But it is not clear from the name alone, if it had any connection with "variation." Digitized by Google
