Somewhere on skyscript mentions planet in swift motion, how do you know whether the planet is in swift motion? Is the planet always in swift motion immediately coming out of a retrograde or immediately before retrograde? or.....?

Any good source which I can find out more on this topic?

It?s swift in motion when it moves more in a day than its average, and slow when it moves less. The averages are listed here:

http://www.skyscript.co.uk/gl/slow.html

Hi,

Without going too much into modern astronomy let us just assume that the all the planets revolve around us (geocentric model)...

Is the planet always in swift motion immediately coming out of a retrograde or immediately before retrograde? or.....?

Simple answer: no. You cannot use the retrograde-station motion to predict the speed of the planets except in one case i.e. when a planet is stationary. A planet is stationary when it is just about to turn retrograde (from direct) and when it is just about to turn direct (from retrograde). When a planet is stationary the speed is ZERO (not a swift motion!). The planet has to "stop" to turn direct or retrograde, hence the speed has to be zero at that instantaneous time.

If you have the time (and patience!), you can chart the motion of the planets but you must have an ephemeris to do this. Take any planet (not sun or moon because they never retrograde), and list out its daily positions. The unit here will be degrees. Call this column 1.

Then, in column 2 you take the difference of the positions (take the values of the position in column 1 and minus those to the values the day before). This is the velocity of the planets. The unit is degrees per day. When the velocity is positive, it is direct. When the velocity is negative, it is retrograde. When the velocity is zero, it is stationary.
When velocity is zero, where before that it was positive, this is first station (direct to retrograde). When velocity is zero, where before that it was negative, this is second station (retrograde to direct).

Then, in column 3, you take the difference of the velocities (take the values of the velocities in column 2 and minus those to the values the day before). This is the acceleration of the planets. The unit is degrees per day per day. When acceleration is positive, the planet is speeding up. When acceleration is negative, the planet is slowing down. When acceleration is zero, then you have maximum velocity (swiftest motion)!

Caveat: The motions of the planets are not regular, hence... well you know!!!