Quote: I'm now using a full sized plaster tool with glass tiles, using center over center strokes. The last grinding session I did didn't change the high zones much. May be a little.
20" homebuilt truss dob 6" watson refractor
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: The rubber expands while tightening, therefor snugging the blank...... Would it be useful to do a sharpie test at this stage?
Quote: Roc was at 74, needing 84. FL was 55 needing 42.
Jc ATM 10" F6.1, 1/25th wave spec (max wavefront error +/- 1/12.6 in zone 4 of 6, sodium light ), 6" F7 spec, 127mm F9.4 achro Refractor, Criterion DX8, 10 x 50 bin, SP mount/Synscan goto. ETX80 (finder) Canon 20D, PST DSI 1, Butenschön 125mm F13.4 refractor, diy spectroscope and curiosity