Autoguiding during autofocusing ?

i have never questioned it but mine always pauzes guiding during AF, just the way the software was setup from the start.

Usually you stop guiding during AF.

Here are two points to consider:

1. It makes AF more precise and more reliable, but this also depends on the disk size, step size and you tracking accuracy. As long as the guiding corrections are very small compared to change of disk size it is not impacting. Also taking more than one exposures per focus point can mitigate the guiding effect. 

2. But what is more important: how do you guide? OAG or dedicated scope? If you use an OAG you have to stop guiding, whereas if you use with a dedicated scope it might be OK to guide.

But anyway: try it out. Run AF multiple times with and without guiding and compare focused positions. This gives the answer for your system.

CS
Rüdiger

I use N.I.N.A and it stops the guiding (PHD2) .

Olaf Fritsche:
The question would then have to be which of two interference effects is greater: 
1. if the corrections due to autoguiding are greater, it would make sense to turn it off during focusing. 
2. if the tracking errors are larger, autoguiding would support correct focusing.  

Does anyone know which confounding effect predominates with good PA? 
Or am I making some kind of thinking error?

Typically autofocus exposures are on the order of a couple of seconds (for my fast F2.2 system) and probably not much longer for most since I get quite a lot of stars using a guide scope.  This may be different with an off axis guider.  So unless your polar alignment is really bad, your drives are really balky with much periodic error, or something of the like, then I think turning it off is thought to be the safest bet.  The way I set up my guider is to use 1.5 or 2 second exposures from my guide camera and then the software makes an adjustment via a pulse to the mount.  So think of it this way; if that pulse happens to occur during one of the main imaging cameras 2 second exposure, then the stars may all be streaked, even much more than from some slight tracking error.

Also, consider that if misalignment is not good and the errors are consistent, then short streaks would result.  But if you think about it, this is not fatal because the HFR or other determination should still find the "best" number, which is all relative anyway.  So still in focus.

This makes sense to me. Thank you, Alan!