Hi Malcolm, > Can someone please tell me where I can find a Foucault Programme to help me > with a 20inch f4.8 mirror with a 9 zone mask. The ones that I have found > only go up to 12inch mirrors with 5 or 6 window mask. Figure can be found at: http://members.aol.com/aplanatic/figure45.htm Best of luck with your 20" mirror, Dave Rowe