On 9/5/11, erikhansen@thebluezone.net <erikhansen@thebluezone.net> wrote:
I was mainly referring to mylar films.
Baader is mylar. It's just manufactured much more carefully than the older material. Truthfully Erik, if someone is contemplating a mylar filter, Baader is the ONLY choice these days. Everything else is inferior. I found the technical sheets that Astro-Physics supplies with it, over the weekend. One thickness is all that's needed, and it is diffraction-limited with only one layer. Any other old-timers remember the "Sahula System" of using non-aluminized mylar to cover observatory openings in cold weather, for night-time use? More notes on plastic solar filters: If you want to make a small, dedicated white-light solar scope, you can install the filter material JUST behind the objective. It must be in contact with the rear element of the objective, to avoid any concentration of energy, which would of course risk damaging it and causing eye damage. This location removes any concern of damaging the filter in normal use. When making your solar filter, do not pull all the wrinkles out or put the material in tension. Even a lot of wrinkles does not harm the image, but excessive manipulation or tension can damage it or shorten it's lifespan. Do not squeegee it like window tint, as that will damage it as well. I found my binocular solar filters late last night and will post pics of them soon. They are also made from PVC pipe. Alpine Stringham has a set I made for him some years ago. Are you on the list, Alpine? The same construction as the one for my 70mm f/10 refractor "Weightless" project from S&T. I also have a molded fiberglass cell for my 6" f/8 Newtonian that is 98% complete. I just have to install the felt liner and the Baader filter material itself. Pics of that soon. Some of you may remember my "Pocket Solar Observatory", a 12x25mm binocular with individual Baader filters fitted over the objectives. Pics of that coming soon, too. If anyone is interested in making a small refractor for a white-light solar scope of similar image scale to the PST and other popular commercial H-a scopes currently in wide use, let me know and I'll be glad to help you put a kit together, making the cell and tail-piece on my mini-lathe. Or I can give you just the objective and turn you loose.