It is not a “First move” option, rather a “Reverse direction” option, it is just a matter that reversing the direction of the Celestron motor means the first (And last) focuser moves will end up with the backlash compensation applied to them, rather than all the intermediate moves requiring it.
Unless they have added it to a later version than I have been using the option is not available in the Celestron driver, you need to do it in SGP, which is as simple as ticking a checkbox then making sure your backlash compensation is still being applied in the right direction and changing that if required.
Yeah, in SGP it is very simple to click on it. The explanation in the manual on what it does was not clear. I will try it as soon as I have the replacement motor on hand and clear skies overhead.
I have not got my setup near me to look at, just click on reverse direction and make sure that an “IN” move according to SGP is rotating the focus knob anti clockwise (Moving the primary mirror toward the secondary) Then I cant recall which way you need to set the backlash compensation, but it should be set so that a clockwise move of the focus shaft (“OUT” according to SGP if the direction is reversed) is followed by a counterclockwise one to move the mirror against gravity. If the new version of the Celestron motor still has 1000 steps per rotation of the focus knob, I would set the backlash amount to at least 500 steps, and probably more like 1000.
Set up that way, a focus run in SGP (With 9 data points) should be:
Clockwise to the initial position with a backlash compensation move
Counterclockwise
Counterclockwise
Counterclockwise
Counterclockwise
Counterclockwise
Counterclockwise
Counterclockwise
Counterclockwise
Clockwise and then a backlash compensation move to the calculated focus position.
With backlash compensation applied correctly but the direction not reversed, all except the first and last moves will have compensation applied and if nothing else the focus run will take 15-20 seconds longer at least.
Will try it out when I get the focus motor. Thanks a lot.
Farzad