Thanks very much for your help, much appreciated. I tried it last night (1st clear night for weeks…) and unfortunately could not make progress. Here’s what I did:
Used nebulosity (Craig Stark s/w) and did a fine focus so I knew focus was pretty good. Noted the focus position on my microtouch focuser (30174)
10 second exposures, asked for 13 points, step size 100. Ran autofocus and it produced a scattergram of points. Resulting focus point wasn’t focused…
Without going into all the detail, I tried various things with step sizes of 10, 20, 40, 150, 200 all with more or less the same result.
Also tried starting slightly out of focus, but that was unsuccessful too.
So a bit stuck really, just focusing using nebulosity fine focus tool at present.
Any further help greatly appreciated.
My scope is a Celestron c11 at f6.3. The focuser is a feathertouch with microtouch attached for control. Using the buttons on the controller, I can move in and out of focus from both directions, so I know the focuser is working. Also from within sgp control panel I can press the software coarse/ fine in out buttons and the focuser works.
One thought I have, is, perhaps the SCT mirror is not settling enough between exposures in order for the autofocus routine to acquire good quality star images for its calculations?
I have this vision of the next exposure being started before the mirror has settled. Having said that, it is a minute movement, so I am probably clutching at straws.