Thanks Bojan, those are Hot mirrors and the one I want to use is a Cold mirror.
http://www.edmundoptics.com.sg/optic...mirrors/64449/ I hadn't noticed the flatness though, 6 lambda doesn't look too good.
Peter, I'm impressed with your results. I have always had problems with focussing, using @Focus2, with 3 different focusers and would certainly go your route if I was a bit more that an OAP. I haven't got enough back-focus on my FLT132 but should have enough on my RC10C. I looked at the information from Innovation Foresight and wonder if I could go part way with DIY and then purchase the FocusLock software to control it all. I've got the Vixen Flip Mirror on the way and will see what that looks like before buying too much more.