Pranam Mavv
Here is wiki link that might help you to understand the retrogression "MAYA" with technicalities even for the inner zone planets. I hope you find it usefull.
http://en.wikipedia.org/wiki/Retrograde_motion
"Asthangat", as per my little knowledge it is a (recharging) state of a planet. During this period (diff for each planet) the planet remains (appears to be ) stationary. This is the case when the planet get out of the retrogression and is to get into motion. So its the buffer / recharging state before the planet gets into normal motion after huge amount of efforts put during retrograde motion.
warmly
Asro