The Indian astronomers were interested in the computation of eclipses, of geocentric longitudes, the risings and settings of planets,which had relevance to the day to day activities of people.
Did not Emerson say?
“Astronomy is excellent, it should come down and give life its full value, and not rest amidst globes and spheres “.
They were not bothered about proposing Models of the Universe and gaining publicity. But then they did discuss the geometrical model, the rationale of their computations.
The above diagram explains the Geometric Model of Parameswara, another Kerala astronomer. Paramesvara and Nilakanta modified the Aryabhatan Model.
By Sheegroccha, he meant the longitude of the Sun.” Sheegrocham Sarvesham Ravir bhavathi “, he says is his book Bhatadeepika . For the interior planets, the longitude of the Sheegra correction is to be deducted from the Sun’s longitude, Ravi Sphuta to get the Anomaly of Conjunction.
The Manda Prathimandala is the mean angular motion of the Planet, from which the trignometric corrections are given to get the true, geocentric longitude.