i recommend you use 6061-T6 alloy(plate), or 6061-T651 alloy(tube etc.) which is the mosr readily available alloy. it is hard, free and clean machining, corrosion resistant, and will be easy for you to get and machine. after machining, if you can hard anodize it black, that is best, but if you cannot, a good black permanent marker will make it ready for use without bad internal reflections. if you have the equipment to measure it, make the cell I.D. about 0.005 inches larger than the lens diameter. you want a snug fit that will not allow the lenses to be off center with respect to each other. if you can cut threads for a retaining ring, make them large, say 16-20 threds per inch, and loose. if not, a retaining ring with smll screws holding it in is ok. the retaining ring should never be tight on the lenses, light finger tight at most. if you shake the cell, if you hear a very slight jiggle, it is probably ok, mostly, the lenses should be retained but not squeezed. good luck, tom leech

• RE: RE: Refractor cell design - tom@digitalmoon.net - September 6, 2000 - 06:45 UTC