Andrew,

I experience similar irreproducible results. Sometimes it works flawlessly, sometimes it just doesn't get there. In most cases where it does not work, focusing on the wrong star is the problem. It selects a nebulous object, a double-star, or just a way too big star. So rescue method 1 for me is manual selection of a small star.
Subjectively I seem to have slightly better results with polynomial vs iterative method.
But I'm also recording my focuser position at various outdoor temperatures and find that the relationship is linear and very predictable. So for my setup, a drop in temperature of 1 degree celsius equals focuser in by approximately 80 steps. Important to keep circumstances similar (system must be in equilibrium with environment and dew heaters need to be in same position.
I do not let the focuser run unattended, and if I'm in a hurry, or experience issues, I just set the focuser where it theoretically should be with pretty good results.

Read More...