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Old 17-03-2015, 08:22 AM
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frankly1 (Frank)
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frankly1 is offline
Join Date: Oct 2010
Location: Weyba Downs, Qld.
Posts: 34
Hi Raymond,
yes the edge is rolled, but I always buy the glass with an extra inch of diameter so as not to get caught up in trying to achieve perfection. Fig XP does show it as rolled, more like a cliff really, than a gentle roll! Ronchi tests showed sever edge roll also, so I rebuilt my mask to reflect 460mm diameter and continued figuring until the results were OK.
I completed a 17" mirror a few years back, got reasonable numbers with 16" of it, and thought - I'll just try to go a little better. After another year I got back to where I was before I fiddled!! Don't want to repeat that as I am at 1/20 lamda at the moment.
Just built the lower box for the mirror to Plop specs, need to finish it for the Queensland Astrofest!!
As for your project, please post some details as things progress, I would like to make a shorter one as well. What thickness glass is your one? Mine started out as 25mm and ended up as 22mm due to more grinding due to an edge issue.

Last edited by frankly1; 17-03-2015 at 10:46 AM.
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