Automatic Focuser for SCT

[schmeah]

Hi all. I have a new Celestron Edge 9.25 for imaging, with a QSI 540 wsg, SX Lodestar on OAG and avalon M Uno mount. I am looking for an opinion on automatic focuser solutions for the Edge and wonder what the rest of you do. I would like to continue imaging unattended. Presently I have perfect spacing / backfocus and balance with a standard Celestron T adaptor and small spacer. 

While I have considered a motorized Crayford type focuser, I would rather not mess with the backfocus and weight, and would like to have flexibility with backfocus in case I decide to add a FR (I have the AP CCDT67) or rotator. Therefore I would like to add a stepper motor to the primary focuser on the Edge for automatic focusing. Options include a Feathertouch with Micro Touch autofocuser. or a new FOCS automatic focuser from Avalon, which is a cheaper solution as it doesn't require upgrading the primary focuser and connects directly to the StarGo software.

My question is: With an automatic focuser on the primary focus knob, presumably you shouldn't use the mirror locks. I have been told that this isn't a problem when using an OAG (no flexure problem related to mirror flop). But does leaving the mirror unlocked create other problems such as excessive focus changes from mirror shift over the course of the evening, that cannot be compensated for by the automatic focuser? I plan to use SGP for focusing software.

Thanks,

Derek