Fuzzy bright stars with my Celestron CPC 1100 XLT

Question

When looking at the brighter stars I cannot focus them to a sharp image. They appear fuzzy. Image of a star test on Vega attached (taken with a Watec 120N webcam). Diffraction rings are sparse and mottled. Does not really indicate that scope needs collimation. Can you help please.?

Thankyou

Mike Brightmore
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