There are certainly a lot of existing designs that would be more practical and easer to constuct. The light is going to have to pass through the corrector twice once from a steep f:4 cone and then next about an f:12 cone. I doubt there is a prescription less than six elements and 12 surfaces that will give satifactory results. Your secondary will not work well that small anyway as there will be a tremendous loss of field. I would image looking down such a system, one would find a small illuminated area surround by a big black tunnel of vignetting. I have seen a sytem with a flat secondary infact I own one come to think of it and it does just what I said. It does not have the corrector but in its place is an electron imaging tube. When used with optics instead of the tube it is about like looking through a 1/4 mile long tunnel.

Is there a reason for this suggestion or are you just "toying" around with ideas? By placing the corrector right infront of a sperical secondary one can acheive good results with a double or triplet (AR coated of course).

Have Fun,
-Rick