[g__day (Matthew)]

Paul,

Can you try moving the guide star around the full frame of your guide program and informing us if the shape of the eggy guide star changes?

I have an OAG with a DSI II Pro Mono - stars were eggy on the full half of the frame that was closer to the OAG and round on the half that was further from the central light path of the OTA.

I should have seen the opposite - which revealed to me it wasn't coma - it was mis-alignment of the optics! CCD Inspector confirmed this - I had massive tilt - turned out one of the screws of the OAG was still tight but the whole OAG had shifted down about 2mm out of true

Maybe try the 30 day evaluation of CCDWares CCD Inspector v2.1.6 and see what it thinks of your main imager and your OAG alignment.

Lastly you can guide successfully with eggy stars - but its hit and miss (at best a 50 - 50) affair in my experience. Not something you want to put up with. Definitely diagnose the source of the issue and get it sorted if you can.

Matt