Attached Link: http://www.thebest3d.com/dogwaffle/whatsnew/3_6/motion_tracking.html

The new update 3.6 of PD Pro has a neat motion tracking feature in the brush Keyframer. If you have a plain sun rendered without much post like flares or streaks and halo, and want to add some post-mortem, you can manually keyframe the path of a brush which contains the image of the flare. That's tedious though if the Sun or whtever you're tracking is doing a zigzag on you, like during a turbulenmt descent into the atmosphere and crashing or hard landing.

Automatic motion tracking can help.

http://www.thebest3d.com/dogwaffle/whatsnew/3_6/motion_tracking.html