Quote:How often and how long do some of you folks cold press when getting close to the final polish and sphere? And, while we're at it, parabolizing?
20 inch f8 Chief Ed Jones designed and a 17 f9 Zanbuto Wide Band Chief Mike Jones designed .Both unobstructed telescopes .
Quote:I take it one step further and am pretty much neurotic about pressing any time I am working toward a figure.
Living at a dark site, I make scope when I have the inclination. I also do woodworking, cycling and other outdoor activities
Active instruments: 4.25" f/6 Newtonian on altazimuth Springfield mount with crutch tripod -- telescope for the handicapped. 12" f/6 Newtonian Telescope maker since 1958; always more to come? Well maybe just one more and it will be something very special Stellafane Awards: 1977 1st award for 4" f/6 refractor 1978 1st award for 4" f/4 Lurie Aplanat 1983 1st award for Newtonian smoking pipe For Sky and Telescope articles, please see Bio info.
Quote: Quote:How often and how long do some of you folks cold press when getting close to the final polish and sphere? And, while we're at it, parabolizing?I never cold press - it's a waste of time. I warm press as required using heavy pressure for a short period of time. The only time this can be a problem is working plate or similar glass, where it can raise the area you're using for pressing, which would result in planing that off if you set to work too soon - in which case you let it return to working (room) temp, for which room temp water works fine.The polisher needs to conform to the work, but there's no magic involved in making it do so, nor in maintaining this contact through any needed working period.Best,Mark
Ed Jones ........... The best data is an interferogram, the best analysis is from an honest optician.
Quote: I only hot press to get the pitch to the right curve, after that I only cold press. For safety I usually cold press dry with a sheet of thin plastic (5 micron) between the mirror and lap to prevent sticking.
Mike Lockwood - Owner, Lockwood Custom Optics. 20" F/3 MX Starmaster, 14.5" F/2.55 self-built Newt., nine self-built scopes, 4.25" to 30" http://www.Loptics.com/