Posted by Robin Vann at 16:06 on 2010 Sep 11
Thanks again Andrea.Yes, I have thought of shimming it but thought I would use a piece of rubber. Thus one could ‘squeeze’ the rubber as one tightened the focuser nuts back into place and have some variation by way of the degree of tightening, rather than having to calculate the thickness of shim required.And yes, the cross-hairs move relative to the centre marker on the primary as the focuser is moved in and out. However, the focuser is fitted with a locking screw and locking it prior to observing results in the cross-hairs remaining centred whatever the position of the focuser.I think we can close the issue now. Thanks to David and Andrea for your ideas. I feel confident about taking this forward myself now.