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MPCC and compression-ring focusers
Using a MPCC with a Moonlite focuser has become a PITA for me lately. The problem was with the width of the flange on the threaded end of the MPCC. It is just a fraction too wide - which has meant that when I try to insert the MPCC into the focuser with the locking ring flush against the lip of the drawtup, the compression ring is just high enough to foul the little flange. So when you try to tighten up the 3 screws on the focuser, it forces you to withdraw the MPCC afew mm in order to get the compression ring to sit properly. The reult has been the MPCC and with it the imaging train behind it is not necessarily sitting true - resulting in some image tilt.
My cure is to put the MPCC in the lathe and turn off about 1.5mm of that flange leaving only enough to act as a backstop to the lockring (about 1mm). The result is I can sit the MPCC in the focuser with the flange flush up to the lip and therefore giving me a stable and flat connection for my cameras.
The attached drawing is not to scale but it probably says what I have done.
Might be of interest to others so here it is.
Peter
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