Calibrate two Cameras OpenCV

I'm using OpenCV 2.2 and I'm trying to calibrate two cameras to view along the same co-ordinate system. The two cameras will be placed a little separate from each other. I understand calibrating intrinsics for a single camera, but am a little confused so as to how I'd be able to combine two cameras together. Follow up questions are good too.

Cheers.

EDIT - Am working on this problem - will post and describe what works for me when I get it done.

Suppose you have two cameras C1 and C2.

1. The fundamental matrix F defines the relation between the two cameras, that means given an image point x1 in C1 how it constrains the position of the corresponding point x2 in C2. The answer: x1 defines a line in C2 and x2 must be on this line. That is epipolar geometry. It is defined just by the cameras parameters and it does not depend on the scene geometry at all.

2. Suppose now you have the two projective matrices, P1 and P2, ie, you know all parameters for both cameras. If you have a pair of correspondences, x1 <-> x2 (x1 from C1 and x2 from C2), you are able to estimate the 3D location of the point X in space that was imaged to x1 in C1 and to x2 in C2. You are able to reconstruct your ball, getting a 3D model. The tricky part is to find the matches x1 <-> x2.

Now, if your problem is to know if C1 and C2 are seeing the same thing, maybe your problem is not a stereo problem, but a recognition problem. Maybe SIFT or SURF algorithms be a more appropriated approach.

Possible dupe of this? My answer from that is StereoCalibrate will allow you to solve for the essential matrix which you can use to relate any point in one camera to a point in the other camera.