Vedic Astrology is based on the Geocentric Model – It means everything is measured taking Earth as the center while in astronomy this is not true. In Vedic Astrology, we consider the apparent path (not actual path) of planets in prediction which is relative to earth.
You can have a look at the below picture for better understanding.
Assume, yellow Sphere is Sun, the blue one is earth and the red one is Mars. None of them (Blue or Red) are moving in the backward direction, it’s their projection on Zodiac Belt which appears to move backward.
In Western astrology, people use the Heliocentric Model – Sun is assumed at the center and then it is practiced.
Effect of Retrograde
The effects that I have encountered practically and observed is that retrogradation only intensifies the malefic/benefic effect for those areas where a retrograde planet has influence
I would say that Retrograde Planet does not give ill effect, it multiplies both benefic effects and malefic effect by a certain factor. A planet getting classified into benefic and malefic is a function of how it is placed with which dignity in the birth chart.
One can place an order for Kundali Predictions to know the accurate impact of retrograde planets in your life. We have modeled and trained ten thousand horoscopes with the help of machine learning. This has helped us in practically qualifying the influence of a planet in our life.