I, for once, am not chasing aperture! I'm chasing WIDE FIELD VIEW!!!
Maybe if you read the following experience of mine from a week ago will give you some insight on my thinking:
http://www.iceinspace.com.au/forum/s...ad.php?t=92811
What I now see that I've omitted in my original post is that a with an 80mm f/5 scope, & a 2" 35mm 68deg FOV EP will give me a huge 6 deg FOV! My 11x70 binos have 4.5deg FOV. I'm now GREEDY for more!!!

To go large aperture, & longer focal length is a step backwards.
I've found a 100mm f/4 achro lens on the net. Would stopping it down to f/5 help?
Adrian, I found the view through my 11x70 binos absolutely staggering. Maybe it was the RFT nature of them, but I can't see myself going for an f/6 and slower scope. That's why I'm asking about the pain that's involved with fast refractors. RFT's have really gripped me, & now I also want WIDE