10"f5.3 Newt (homemade) 8"f6 (hm)8"f7.5 (M Harry mirror) 6" f8 Newt (hm) 2 4.25"f11 Edmund newts. 4.25" Schief (hm) 5" D&G Refractor 5"Celestron MakCass, 6" MakNewt Intes optics,6" f10 MakCass Intes optics several small refractors 90mm, 80mm, 60mm
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:I found a couple of SK5 lens blanks that I had bought and forgot I had. Plano concave, about 110mm dia, 18mm thick. Other than the fact that they are a heavy crown glass with a higher index of refraction, they don't seem to be anything special. I am thinking about using them for grinding tools as I don't have a lot of money tied up here.Anybody out there who can suggest a better use for this glass? Thanks for any ideas.
Quote:I don't know if they are suitable for a "Houghton" but it may be worth checking it out. I came across a bunch of BSC2 crown glass a few years ago and have plans for a 6" Lurie-Houghton f5 in the near future.
Refractors Reflectors Two Cats A few eyepieces
Quote:Those SK5 blanks -- I looked SK5 up in a glass catalog and they are not ordinary crown, but Special Crown, and not in the ordinary run of crown glasses. I'd advertize these and some sharp cookie will be glad to have them. I think that a very fair price for each of them, but others may share their thoughts.And the sharp cookies are all over the place in this forum!
Quote:Well, you could pop for a blank of Ohara S-FPL53 and make this apochromatic lens. 100mm aperture, 1000mm EFL, corrected over the 0.4358-0.6563 µm spectrum and 20mm diameter FOV.
Quote:Your estimate on the BK7 cost might be a little high. I was thinking more like about $600-$700 for a 110x16mm S-FPL53 blank. Should get a real quote from Naked Optics or Newport on it before scaring the poor guy with sticker.
Quote:Just shoved sk5 into a Kzfsn4 combo (ATTACHED)and it is much better than the standard doublet combo. Not optimized, as in the OSLO attachment in the previous post. Some combo with SK5 must be worth pursuing...