The above was taken with EdgeHD11 viewing a field of stars in the milky way at 2s exposures with C filter.
The seeing was very good so the curve is well defined and goes down into the low 1" fwhm range.
If the seeing is not as good the curve will be much flatter and you might need to use a larger step size. So the ideal settings will depend on many factors. This is the shape of the curve I aim for - so that it shows the curvature near focus and lets you get a sense of the width of the "in-focus" range - which in this case is about +/- 3 steps.
Other people aim for a very sharp V - but that loses a sense of the region near best focus - and when it's done you can't tell how well it 'hit' the best value.
Frank