Computational Modeling of Retrograde (Vakri) Motion and Ceṣṭā-bala in Parāśarī Jyotiṣa: An Astronomical Formalization and Knowledge-Engineering Treatment
Pranav Anand¹ and Anand Vadakepat¹ ¹ RetroGrade, Jothishi Online and Advertising Services Pvt. Ltd., Bengaluru, India Correspondence: research@retrograde.co.in · https://retrograde.co.in Abstract Retrograde (vakri) motion is one of the most interpretively significant — and most frequently misapplied — constructs in Vedic astrology, yet consumer astrology software typically reduces it to a boolean flag. This paper gives a precise, reproducible treatment. We (i) formalize apparent retrograde motion in the geocentric ecliptic frame, deriving the station condition and the synodic timing of the retrograde arc for the classical grahas; (ii) formalize the classical quantification of motional strength — ceṣṭā-bala — within Parāśara's ṣaḍbala scheme, and relate it to the eight-fold gati taxonomy; (iii) present algorithms that determine retrograde state and compute ceṣṭā-bala directly from an ephemeris; and (iv) describe how these primi...