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Actually I realise I have got one thing backwards a bit, if you racked the focuser "Out" more steps than it actually takes to get all the way out, it will then be further "in" than expected.
Crayford focusers slip by design, if you rack the focuser all the way in or out, you can keep turning the shaft and it slips on the drawtube as they are friction driven. The trick is to ensure that you have enough tension on the shaft that it does not slip when racking the focuser in (As that is normally against gravity) or slowly slip downward with gravity when the shaft has not been moved, bit not so much as to make it hard to operate.
If there is a focus lock/brake screw, this needs to be loosened right off or it will drag and make the focuser slip. There will prbably be other tension screws that set the tension of the shaft against the drawtube but I would have to look up the Eon, I am not familiar with it.
The other end of the scale is a rack and pinion focuser, they do not slip, but if you drive them past either travel limit you can damage the focuser or the focus motor!
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