Thanks for the advice everyone.
After 5 weeks of rain here in Melbourne, had another go last night using M41 as the field.
The secondary appears well centered - checked it with a newtonian laser and the laser hits the secondary right in the middle of the donut marker.
https://www.flickr.com/photos/johnka...posted-public/
https://www.flickr.com/photos/johnka...posted-public/
What are people's thoughts in terms of the defocused star field attached?
If anything, I am thinking the centre of the field is slightly more above centre/right of the taken image - so would have to move the image slightly down and left, but other then that seems quite symmetrical to me. Any adjustments I am making I am doing using only the secondary at this stage and have not touched the primary at all.
Look forward to advice.
John K.