I'm working on a photogrammetry project with a sphere of image like this : 
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For each ray I have its origin and its direction such as : r(t) = o + dt.
And I need to relatively quickly compute the center by estimating the intersection of the rays of the camera direction (Z rays). It doesn't need to be perfectly accurate.
As I used SVD for triangulation and to compute homography matrices, I was thinking on keeping it that way (I don't know if it's possible with 180 entries) but I don't know how to compute the equation Ax = b with the information I have. Or is there any python library allowing you to compute this intersection?
Could you please help me?