Thanks to everyone for the suggestions. Based on past experiences with this motorized focuser, live-view DSLR and bahtinov mask, my "feel" for the backlash would probably be about 200, but perhaps I am underestimating. Last night I tried increasing the backlash compensation to 500 and things seem to improve. Some were near perfect:
while others were still not quite so:
Next time out (hopefully tonight) I'll try something larger like 750 or 1000.
Some additional questions:
1) Sometimes, the last point on the left is "out of alignment" (middle graph above is a good example). Is this also backlash or possibly something else?
2) Is there an easy way to identify which way (ie. In or Out) is counter-clockwise? I'm assuming I've got it right or my graphs would be much messier than they are now? I guess this is something easy enough to test ...
DaveNL
PS. Overall, I'm pretty impressed with this autofocus thing.