Find semicircle of a ball
I am capturing a high speed moving ball. As I have shown in picture its getting blur because its speed. I need to find its radius. Now am finding radius using enclosing circle of contours . But sometimes, due to motion blur it is returning larger radius (left side first image) than normal radius(middle image). Can we detect semicircle of that blurred image like in third image. So i can get exact radius by this method? Also I need help in approaching this method. 
Mab be this paper can help you