Determining the value to put in for focuser backlash compensation


What has worked for me is to make sure that when AF runs it goes out of focus three times the in-focus value. And I set the backlash comp to stepsize+20%. Works on both my rigs.
If you have step size too big (and on the AF run the out of focus first sample is say 5-10 times the in focus value) the samples are too far apart to find the true focus point. IF you have too big a step size you tend to get a shallow ā€œUā€ or a bowl shape curve as opposed to a sharp V. But too small a step size and you can fail to get AF to work at all. You just need to play around with this and watch the curves.


Here is what I came up with for the setup I have. Edge HD 1100 with Micro Touch Focuser.