Mathematical model as per the algorithm of Sūryasiddhānta for computation of location specific true position of the planets

Sūryasiddhānta is an important astronomical treatise, which is very popular even now in the entire Indian sub-continent. Like other astronomical texts, Sūryasiddhānta describes the procedure to compute different astronomical parameters. However, the procedure to compute the planetary true positions for a given day (as per mid-night reckoning system) and place need to be applied independently for different planets. In this study, we are presenting a mathematical model for the computation of the true positions (nirāyana longitudes) of the planets at any given instant of time of the day for any desired place. This mathematical model is based on the algorithm presented in the Sūryasiddhānta with some modifications such as the usage of the fractional part of the ahargaṇas. The planetary positions or the longitudes of the planets are computed for the Sunrise of Mandi, Himachal Pradesh, and are compared with the Stellarium values (nirāyana – Nirāyana longitude values are obtained by applying the Precision of Equinox correction to the Stellarium Ecliptic (sāyana) longitudes.) to study the accuracy of the results obtained from the mathematical model.