Parahitakaraṇam: A medieval formulary manual in the Kerala vernacular for calculating planetary mean longitudes

Abstract

The Parahitakaraṇam is a fragmentary astronomical text of unknown authorship, existing only in a single palm-leaf manuscript whose date of composition is also uncertain. The text focuses its attention on one single step in the computation of planetary positions, that is, the calculation of planetary mean longitudes. Nevertheless, it presents several interesting issues. The text is also engaged in conversation with a canonical astronomical text of the Kerala genre, the Karaṇapaddhati. This paper provides a translation of the source text. Mathematical notes and worked examples are also provided to illustrate the computational process, which encodes several variations, sometimes quite subtle, in the case of each planetary computation.