The only post I can find in this subject in internet is on Cloudy Nights forum and the author stated that he achieved excellent focus with spacing 56.2mm. I have added in 5mm T2 spacer between the filter wheel and camera to achieved 36-37mm between camera and field flattener. The camera adds 20mm between sensor and end of flange so this makes total of 56-57mm, which should therefore be ideal. I will find out when I next have a chance to use it at night!
I’ve changed focal reducer for the dedicated Sky Watcher one – it came up on AB&S second hand. Reason for doing this is that the Equinox had great difficulty gripping the Tele Vue TRF-2008 field flattener and it kept slipping – this isn’t problem with TRF but rather with this particular combination. New field flattener grips tightly and daytime tests suggest comes to focus but I don’t have far enough away tree to know for sure whether enough back focus so I will find out next clear night……if not enough back focus then I will need to cope with TRF which will focus. Mind you this is the dedicated SW one so it should work!
I have connected the field flattener to the telescope using a bespoke 2″ nosepiece purchased from First Light Optics. I think the end of the focuser tube might unscrew to allow direct connection by screw thread of flattener to scope but I can’t get it to budge and I am worried that I might damage the scope if I try harder to get end off the draw tube on the focuser.