Paul : I can try to use short exposures with the system defocused a little to sort out collimation.. Will definitely give it a burl, because at 25" out, no wonder the data looks a little damp..
Its funny because the diffraction rings were concentric and evenly spaced.. the scope gave razor sharp views through the ep.. stars resolving into tiny little spots of light right through the FOV... the only thing I did notice was a shadow around the edge of the field of view on one side of the EP.. But how could the diffraction pattern look collimated if the mirror was so poorly tilted as to cause a shadow like that? I dunno.. will have to look at it further..
Alex.