Thanks everyone.
The odd diffraction spikes are caused by part of the pick off prism assembly of the off axis guider protruding into the light path, a trade off with that and getting the prism and camera as close to the secondary as possible.
Flat fields are shots of a nice diffuse white object like a wall of large piece of cardboard that can be used in software to remove vignetting and other blemishes, in this case I didnt use a flat as I need to come up with a better way of taking them, putting paper over the end of the scope doesnt work as I get odd shadows that dont appear in the light images. This looks to be a good way of taking good flats.
http://www.ghg.net/cshaw/flat.htm
Scott
