Focus between eyepiece and camera

[Adam Y]

OK I give up - I can't seem to get into my pea-brain long enough to remember when it would actually be useful.  Is there a standard for which way to turn the focuser knob after I've changed from the eyepiece to the camera?  I end up going back and forth so much I forget where it was originally positioned.  It would be helpful if there is a way to know for a given eyepiece/camera combo which direction I'll be turning (all other things being equal).  

 

Just looking at it, with the eyepiece first and then the camera sitting in the diagonal, the plane of the eyepiece lens sits about 20mm further back than the plane of the sensor.  So I believe I can get close with parfocal rings (at some point when I have them), but assuming the above condition and no rings on hand - would I turn clockwise or anti-clockwise to shift the point of focus to make up that 20mm difference?  It's doing my head in.

 

thanks!

Adam