Pause autoguiding during backlash comp move

Can a user option be added for this? Last night PHD2 lost the guide star during a filter change which required a backlash comp move. As I’ve mentioned before, this happens in my setup because I’m using a standard (no mirror locks) SCT and a focus motor on the stock focuser, so the image shifts during large focuser movements like backlash comp.


I think the star will be lost even if PHD is paused. IIRC when PHD resume guiding it will look for the star in the same place before it got paused. So pausing will not help with your issue.

Have you tried increasing the search box size in PHD?



When the backlash comp move is completed, the star will be back in (pretty much) the same place it started from, so it will be inside the search box. The problem comes up when PHD2 starts looking for the star before the backlash comp move is completed. At that point, there’s some chance the star will be outside the search box. I already use the maximum size (50 pixels) search box.

Ah OK!

Have you tried to disable guiding while focusing?



You can pause guiding during autofocus runs (which I do), but this does not pause guiding during other focus adjustments, such as filter changes.


Very timely… I had exactly the same issue the other night when the backlash compensation was running through, the guide star became large, PhD lost it and never picked it back up.

I set the box size to 100…

Yes this would be important to me also. In my case I use OAG and MetaGuide - and on filter change if backlash compensation kicks in - the mount should stop guiding and wait for focus to be restored - then start guiding again.

For MG this means PostMessage of the following: MG_RemoteUnGuide, MG_RemoteUnLock, [change filter and focus], MG_RemoteLock, MG_RemoteGuide

But if you are using a guidescope rather than OAG, there is no need for this.

Similarly MG should be told to unlock and stop guiding - then lock and start guiding - before slews to targets - etc. These are easy messages to send and should only impact MG users.


This has been implemented in It is more invasive than I would have liked. Beta users please watch your sequence for a bit before you leave it unattended. The guider pause for backlash (and subsequencet resume) will take place anytime backlash occurs. The only exception to this is if:

  • Auto focus has paused the guider for the entire AF run
  • Backlash is invoked while a sequence is not running (manual actions)