Wow, that's an awsome image Tony, even with the distortion.
Here is a couple of images i took recentlyshowing the same problem big time.
The first image was taken with the 5dh 50mm f/1.4 @ f/3.5 8 seconds ISO 3200, seems o.k.
The second image, taken with the next shot, was 5dh 50mm f/1.4 @ f/1.4
the coma and vignetting have completely ruined the image.
It is amazing what a couple of f stops will do as far as lens capability and image quality is concerned.