Thanks Dean,
That was my first thought Dean but 2 points make me question myself.
1. It must be much more forgiving than a scope as it is only 25 x magnification.
2. If it was 1/4 or 1/2 wave the commercial ones would be a lot more expensive than $280 (mirror is at least 250mmx200mm)
Given the cost differences
I am hoping someone has done it or knows how to calculate it.
