SGP Autofocus vs PHD2

Hi, I am trying to get autofocus integrated into my sequences. Autofocus works very well, but I am finding an occasional problem when I use it at the start or during an actual sequence. The flow is: Start Sequence, Plate solve to target, resume autoguider, pause autoguider, run AF, resume autoguider, start image. Now, the problem occurs when resuming the autoguider after the AF routine and the guide star has moved significantly due to a bit of movement in the optics when focusing. PHD2 seems to struggle to get it back to the centre. It ends up selecting what seems to be a bit of noise rather than a star and guides (ineffectively) on that. My solution has been to stop the sequence, get back on target, restart guiding and then resume the sequence. That works, but won’t be much use if this happens after an AF run in the middle of the sequence while I am tucked up in bed!

Has anyone else suffered this problem or am I doing something wrong and creating this problem?

I am using a WO Star 71 with QSI 683 with OAG. I stop the autoguider during AF as PHD2 seems to struggle when the guidestar goes very out of focus.

I haven’t attached a log file to accompany this problem, but if somebody needs me to do that, please say.


I have found that making the search region in the PHD2 guiding tab larger helps a lot. If the guide star falls outside of the search region during focusing, PHD2 will either fail to guide or try to autoselect a guide star. Making the search region large enough to contain the guide star movement during focusing will generally solve the problem.


That’s great advice, thank you Tim. I’ll give that a go.

Also do not forget to do a bad pixel map or darks in phd2 for your guide cam. It will reduce any chances of phd auto select guide star from choosing a hot/stuck pixel as the guide star.

Quite right @HomerPepsi, I always use darks. Touch wood, it seems to be behaving itself now (oh no, that’s cursed it!)…