[deadsimple (Ash)]

Hi. I recently made a contraption to get my Canon 450D and standard 50mm f/1.8 II lens onto an EQ6 mount by itself, so that I can dive into widefield long-exposure photography. Unfortunately after trying it out I'm getting massive amounts of coma in my shots.

The coma is off-centre too. The top (and slightly left) of each frame is the sharpest, while the bottom right is a complete comatic mess. Stopping down the aperture helps (as expected), but even at f/8.0 I still have coma in the bottom-right 30% of the frame.

I shoot at about f/4.0 but I've included an f/1.8 image with overlay below to accentuate and highlight the problem. Any ideas? This is driving me nuts. I'm going to try other lenses tonight, but I was under the impression the nifty-fifty was meant to be fine when stopped down enough.

Thanks for reading.