Raymo,
Interesting stuff....
If you can get a hold of a webcam (or similar) then Florent Losse's excellent software can be used to measure and analyse the images....
http://www.astrosurf.com/hfosaf/uk/doeva1.htm
florent_losse(at)yahoo(dot).fr
Drop him an email, mention my name and get the latest freeware version.