Ah - UK Orion, you say? And a 10" Newtonian from about 10 years ago? Maybe you have the same problems we had. Bought a 10" from them for a good price around 10 years ago, but could never get a truly sharp image. Tried collimating, waiting for mirror to cool, different eyepieces - the lot. Eventually, and in some desperation, the Missus and I made a pilgrimage to an expert up in the fens, who checked the optics out very carefully. The mirrors themselves were OK - figured to within tolerances - but the setup was wrong. I believe there was nothing that could be done to fix the problem - would have had to completely remount the secondary and probably drill a new eyepiece tube. Finally sold it for a song and moved on to other things... Hope this isn't your problem!