Originally Posted by
Paul Kinzer
As for figuring out whether it's possible, I can do that. I've made more than half a dozen telescopes and needed to figure out the baffles needed for contrast in refractors, and tube diameter/length for reflectors. And my sixteen-year-old son is a math wizard. Even without those helpful advantages, I have the camera already, and a lens that will cover the format (a 300mm Symmar), and another on the way (a 19-inch Apochromat Artar). It should be fairly easy to set up a test bed using the lenses, the camera, a dark cloth, and a sheet of glass or other reflective material, to check the possibilities. Or, again, am I not understanding some key limitation?
Pfsor: My experience with telescope-making has also included finding ways/materials to limit weight. I have on hand some very thin, but very strong 1.5mm thick plywood. Used as sheathing on a hardwood or aluminum frame, it would be very light. I used it on this 14-inch reflector. The scope is over five feet long, and has a circumference of 56 inches, but the plywood added less than five pounds to the weight. The Rittreck seems plenty robust enough to support something that big, though of course the ground glass and film backs add a lot of weight. You may have hit on the limitation that kills the idea.
I am not a math wizard, though, so could someone offer any ideas about whether my idea would make this vignetting worse, or better, or have no effect? Or maybe the writer was mistaken? I could, of course, wait until the 19-inch (480mm) lens arrives, and just check through the test set-up I described. But it will be a week or so before it gets here, and this idea is itchy, and I want to keep scratching it.
I could also make some sketches, or get my son to think it over. But my concern is that I might be missing something obvious that one of the ULF folks might see right off, and my son is busy with never-ending homework, learning some songs for a barbershop performance, and practicing some other songs on his bass (a bit from Jim Croce's 'Operator' has him stumped). He's a renaissance boy!
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