This 20" F3.57 mirror ended up with a focal length of 71.6", which gives a quite comfortably low eyepiece height. The final Foucault test yielded a P-V rating of 1/25th wave on the wavefront, and a calculated Strehl of 0.997 according to FigureXP. As always, these FigXP numbers are overly optimistic and I don't claim the mirror lives up to them. But the surface certainly meets our shop standard of having an 80% probability of testing 1/10th-wave. The mirror is quite smooth, and the zonal measurements easily fit within the Millies-LaCroix "tornado" boundaries.
Included here are pictures of the grinding tool I made for this mirror. Also a photo of my spherometer and a test of the mirror's sagitta. The final picture is the mirror grinding in the fixed-post configuration on my grinding machine.
