Hi Andy
Thanks for full response…
Yes, your image of the spectrum looks like those I was getting before I adjusted the main mirror (i.e. a bimodal profile). I take your point about it being integrated flux rather than some peak value that is important. I will go back and have a look at that.
Your main guide star looks pretty round to me (albeit with the left hand side lobe which appears ubiquitous in these gude images). I’ll try and take some later if possible to compare. The idea of scope focusing using spectral throughput as the measure is also interesting (But I woud have thought that a correctly adjusted guide-assembly would imply otimal throughput?)
cheers
Kevin