Stuart Johnson
John, I think you hit on at least part of the problem. I have a clear filter to protect the lens and sure enough there is a smudged fingerprint. The timer/release is a little infrared button thing separate from the camera. You set the camera to instant or delay release and then click the button. I probably introduced a bit of movement when I clicked it and then tried to hold up the piece of cardboard to block some light.

Thanks everyone for the input. You have all pretty well hit on the same issues and I think I can now get to work trying to correct the mechanics.