Center after focusing


I’m imaging at quite high resolution (0.55 arcsec/pix), guiding using OAG, and finding a problem getting both correct focus and good centering.

The thing is:

  • if I leave the autoguider running while focusing, either (a) the focus is ruined (if autoguider is not waited to settle) or (b) takes forever (if autoguider settles)
  • if the autoguider is off while focusing, depending on the last centering slew, the guide star may go out of the autoguider field (drift due to backlash).

As with SGP full frame focusing being centered beforehand is not really needed, I think first focusing, next centering, is better. At least it is for me :smile:




I’ve always thought about this too. It’d be nice to have the option.

I have always wanted the “Meridian Flip” options dialog box to have the option to auto focus before centering. With a heavy mirror OTA, the meridian flip can cause a noticeable loss of focus. I think auto focusing before centering would improve the plate solve / centering function’s reliability.


Please don’t add multiple requests to the same thread. I am very easily confused.

Also a good feature for me +1

A big “me too” here. I’m in a similar situation to Jamie (am using a C14 Edge at F/11 with OAG and autofocus motor on the primary (mirror shift) focus control. I’ve tuned the auto focus settings so that very often I get successful results. But I can’t completely eliminate the mirror shift, and at this plate scale, even with the biggest search box I can set on PHD2, I sometimes lose the guide star after autofocus - and in those cases PHD2 often picks up a different star. Result - a sequence of beautifully focussed images with the target way off-centre.

The centering routine works amazingly well even at this plate scale - at the beginning of a run, or when manually invoked, it puts the target right in the middle of the FOV, and guide star positioning is very repeatable.

So I’d be hugely supportive of adding the option of a target re-center at the end of an autofocus run.


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For me it is also very important to center after focusing. I think its a problem that almost every people that use automatic autofocus has.
Just to put a box, that we can mark if we want to re-center after focusing or not.

Thanks for all your work,


Yeah, not sure why this still hasn’t been implemented. There also seems to be what I would consider a bug in that it centers and then attempts to resume guiding BEFORE it focuses. Since I use an OAG, PHD2 can’t find a guide star when out of focus, so it always fails!


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Would love to see this also. Lots of lost guide stars, sequence recovery, and wasted imaging time as a result of current sequence flow.

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Yes, this is an absolute MUST! I’m really trying to like the program, lots of people use it with success, most of the problems I’m having are user error, (mine) but this particular issue definitely is a priority.
Thanks for all your hard work!