[ATM] Stupid Fine Grinding Question

[peter at kitgear.com (Peter)]

Hi,

I'm working on an 8" f/6 travel scope which I plan to use this summer to do
some observing in the bad lands of Alberta (you know, Dinosaur country...)

I have not done a mirror for a while, and never one this small and I'm
having trouble getting the mirror spherical as per the sharpie test. The
central region wares away before the edges so I lengthened my stroke to >50%
of the primary diameter with a lot of overhang (1/4 per side). The tool is
segmented and a little smaller than the primary. I don't recall having to
use such long strokes on my previous mirrors.

Any help would be appreciated...

Thanks,

Peter