Martin
Thanks for that.
Unguided Star test
Unguided images are good at 60s.
Pinched Optics ( Defocus Star test )
Slew to a mag 2 Star and defocus the Star into a large donut. The Star or large donut should be circular and uniform and also be able to see the spider vanes and the 3 mirror clips.
Per image the collimation is OK but not perfectly centred particularly in the edges of the image. There are no clips visible as I am using a mask. The donuts on those bright stars (no idea what magnitude - need to do some more homework) look good but the scope is near the zenith now and the problem is not there.
Check Guiding
Dec backlash is causing me a bit of grief with the bigger newt but hasn't effected images to date.
Re check Collimation using both Cheshire and Laser as well
I am using OCAL. I will re-check collimation but not sure this is the problem.
Finally there’s a load of photo examples of optical aberrations with Newtonians online , Stargazers Lounge , Cloudy nights and even on some old IIS posts , they may match something similar to yours
I had started looking but had not yet found anything that helped. Will continue focusing on recommendations above.
I have just captured another image with the scope defocused and it shows a definite trail to one side. Not clear to me whether its optics or tracking. However I am done for tonight but will try and post tomorrow.