15 Feb
2012
15 Feb
'12
3:33 p.m.
Has anyone actually made a mirror from a porthole glass, ala John Dobson? The reason I'm asking is that I just grabbed a piece of glass on eBay, an old porthole glass, 8-1/2" diameter by 3/4" thick, for $29. I've made a few mirrors from both plate and Pyrex, but have never ground and figured an actual "port-hole" mirror.