Hi Robin

#579843
Kevin Gurney
Participant

Hi Robin

To clarify this – the effect I am talking about is brought about by moving the main mirror on its axis using the set screw in the base. In spit of my guiding difficulties (now resolved! – see below) I still had the star in the centre of the slit. I simply had to have the slit well off to one side in my guide image to get the centre  into the sweet spot zone

Kevin