Crayford and Reducer on SCT

[Corpze]

Hi all gazers, i am having second thoughts about getting a crayford for my C9.25 (non HD) and that is because of the 0.63 Reducer / Flattener that i am imaging with. As camera i use the Nikon D7100.

According to my calculations, and what i have read on internet, the optimal distance between the reducer and the chip is 105mm, the only focuser that allows for this distance (107-ish mm) is the feathertouch with the "shorty" sct-adapter witch is 56mm, my nikon T2-flange to the chip is 50mm. The Steeltrack and moonlite is far to long (93 and 91mm)

But, according to some people, i can put my FR after the focuser with good performance, but how would that effect the reducing, and flattening? are there any out there who use crayfords and reducers on their SCT's with DSLR's?

If nothing seems to work, i am getting the feathertouch microtouch replacement for the stock SCT-focuser.

// Daniel

[Peter Drew]

My understanding is that the focal reducer is designed to fit on to the rear cell and then the photographic plane is at an optimum distance from this. The focal reducer, being a positive system acts as the reverse of a Barlow, the further inside the focal plane of the main optics it is placed the shorter the effective focal length becomes.

[Corpze]

Yes that is right, but how much will the focal length change when i move the reducer (for instance 100mm outwards) and the flattening effect as well?