I've believe I just worked out how to calculate the change in apparent position of a moving celestial body, such as a comet or asteroid. PHD2 uses this for tracking comets in units of arcsec/hour to slowly shift the lock position.
Dec motion is easy, it's just the difference in Dec position between two time samples.
Ra motion is a bit trickier but I believe it goes by this formula.
15 x Difference in Ra x Cosine(Current Dec Position x 3.14159 / 180)
My hope is the ability to calculate this within the guide module and pass it onto PHD2 and internal guider for comet tracking. Similar to the way Cartes Du Ciel can. But we can have a find object popup in the guide module to choose the target we wish to follow.
I've also noticed with calculated rates provided by the Minor Planet Ephemeris Service, that the rates can change significantly in a short period of time on fast moving comets. So I also propose periodically updating the lock position shift rate automatically.
Thank you developers for diligently making KStars more and more capable.