Erik
the spacing for theccdt67 is 101mm exactly. you allow 16mm for the FR itself and then the rest of the distance is made up to 101mm. see the following pdf (
http://www.astro-physics.com/tech_su...r-techdata.pdf).
My QHY10 has a 20mm space between the t thread and ccd chip and so adding the 16 to 20mm gives 36 and leaves 65mm spacing needed. I made this up with a 10mm+30mm T spacers and a 25 mm 2" nose piece as in the photo attached.
Hope this makes sense re orientation and spacing. This gives me perfectly round stars with either the qhy10 or QSI583 camera (but for the latter camera I have to remove the 30mm spacer as the chip to t spacing is 50 mm for the QSI583).
Allan