On the calculation of the Moon’s latitude in Indian astronomy

Abstract

The latitude algorithm of Indian astronomy has been a long-standing puzzle. All interpretations of the algorithm by various authorities of the past have failed to produce a reasonably accurate result for the latitude of the heavenly bodies. In this paper we examine the latitude algorithm of the Moon in detail. It is determined that a central cause for the failure is a misinterpretation of the mean-max parameter as specified in ancient texts such as the Sūryasiddhānta. In addition, there appears to be a missing sub-algorithm for the calculation of maximum latitude, a key component in the overall latitude algorithm. After a detailed analysis, we provide a conjecture of what the missing algorithm for the Moon’s maximum latitude may have been like and why it was possibly expunged from the Sūryasiddhānta.