John Dobson gave me some porthole glass that I used as a tool to grind my 22 inch. It was 16" in diameter and worked well until it exceeded the plastic limit on my floor one evening. ________________________________ From: Chuck Hards <chuck.hards@gmail.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Wednesday, February 15, 2012 3:32 PM Subject: [Utah-astronomy] Porthole glass mirrors 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. _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Send messages to the list to Utah-Astronomy@mailman.xmission.com The Utah-Astronomy mailing list is not affiliated with any astronomy club. To unsubscribe go to: http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Then enter your email address in the space provided and click on "Unsubscribe or edit options".