the retrograde or Vakra movement of planets

the retrograde or Vakra movement of planets as could be understood by a layman like me

in astronmic terms we can explain the Vakram very easily..

As per reality as expounded in Keplers law, the orbits of the planets are elliptical..

But in Indian Vakya Ganitham sometimes the orbits are reckoned as circular.. In an elliptical orbit, the transit is slower that the circular one in certain areas where the radial distance is too huge... and this is understandable as per Keplers formulae on planetary motion..

The Vakaya Ganitham of India is usually given corrections through Drik Ganitham.. based on actual observation..

When such periodic variations are observed and the data pertaining to circular orbit as presumed is superimposed by the observed data as per elliptical orbit, (and the data is projected statistically too) the planets which are supposed to be in certain positions in the firmament which are located as Rasis.. Mesham etc.. are seen lagging behind.. or having lesser moving speed that that is expected and the planets are seen in a different Rasi..

For example which Sani is in Thulam Rasi, and is expected to move to Vrishikam with a regular speed, just gets slowed down apparently because of the above phenomenon, and has a relative motion backward and could even enter the Kannya rasi.. which is behind Thulam, and of course after having a relatively backward motion, the planet just stops at a point for a moment and then starts moving in the forward direction..

The point where the relative motion of the planet with reference to the rasi it occupies gets slowed down to give an apparent movement backwards, it is considered that the Vakrata starts..

When the relative backward motion gets neutralized and the movement commences in the forward direction, we say there is Vakrataa nivrutti..

This is too general an explanation.. meant for laymen like us.. The finer calculations have to be left to the astrologers and astronomers of eminence..

In the predictive astrology, Vakrata or retrograde motion of planets are supposed to affect the natural behaviour of the planets adversely..