EmguCV: Detect a ball in the frame
Remove things you don't want

Since the camera is static, you might want to use a background remover first. I found that the standard one provided with OpenCV works pretty well. I create it like this in the Android OpenCV SDK (you can play with the parameters) :

backgroundSubtractor = new BackgroundSubtractorMOG(3, 4, 0.8);


Then, apply it to each image in your video (no need to re-instantiate it unless you move the camera, it will learn from the sequence of images).

Computing the motion

First, using the Hough Transform for fast-moving shapes isn't very useful. The Hough transform requires you to be able to detect the shape's boundary with some accuracy, which obviously you can't, thanks to the motion blur.

I would suggest looking into algorithms for computing the optical flow. I don't know how close EmguCV is to the original OpenCV, but you could try calcOpticalFlowPyrLK (computes the flow for a set of points in the image, usually obtained using the goodFeaturesToTrack method) or calcOpticalFlowFarneback (computes a dense flow for the whole image, but more CPU-hungry).

Additionally, there have been some people working on CUDA/GLSL versions of Lucas-Kanade (the first one) if you really want to have a fast, dense flow algorithm, but I haven't seen a lot of useful implementations.

See the OpenCV documentation here : http://opencv.willowgarage.com/documentation/cpp/motion_analysis_and_object_tracking.html#calcOpticalFlowPyrLK