Brightstar manual filterwheel & SXV-H9, which spacer for MPCC?

[RikM]

I am after a manual filterwheel and many folk have recommended the Brightstar 5 x 1.25" manual wheel. I will be using it with a Baader MPCC in front and an old SXV-H9 on the back. Which extension tube would I need to give me the magic 55±1mm for the MPCC spacing? The camera manual says it has a backfocus distance of 17.5mm but I don't know if I need to add the thickness of the T-T adaptor on to the 21mm quoted thickness for the wheel, so do I need a 15mm or a 17mm spacer?

[Earl]

The first trick is getting the camera as close to the Wheel, after that measure it all up and go from there.