2 layers are recommended with films.
I need a piece 4 1/2 to 5 inches square.
Deloy Pierce _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
On 9/4/11, erikhansen@thebluezone.net <erikhansen@thebluezone.net> wrote:
2 layers are recommended with films.
That would make for a pretty dim image. I'm pretty sure Baader doesn't recommend two layers. DeLoy, I may have a piece that big. It might take me a few days to find it however.
I was mainly referring to mylar films.
On 9/4/11, erikhansen@thebluezone.net <erikhansen@thebluezone.net> wrote:
2 layers are recommended with films.
That would make for a pretty dim image. I'm pretty sure Baader doesn't recommend two layers.
DeLoy, I may have a piece that big. It might take me a few days to find it however.
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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.
On 9/6/11, Chuck Hards <chuck.hards@gmail.com> wrote:
If you want to make a small, dedicated white-light solar scope, you can install the filter material JUST behind the objective.
Just to clarify, this works for refractors, SCT, and Maks ONLY. For SCT and Maks, it must be just behind the corrector plate, with a central hole for the secondary, but be very careful to make sure the seam between the filter material and secondary is light-tight. You can't put it just in front of a Newtonian mirror, at the bottom of the tube, because of reflections off the front of the mylar. Contrast is reduced too much due to bright internal reflections off the filter material. Makes the most sense with small refractors of 80mm aperture and below, SCTs and Maks are overkill.
On 9/6/11, Chuck Hards <chuck.hards@gmail.com> wrote:
On 9/6/11, Chuck Hards <chuck.hards@gmail.com> wrote:
If you want to make a small, dedicated white-light solar scope, you can install the filter material JUST behind the objective.
OK, before someone else posts it, it works for Gregorians too.
On 9/6/11, Chuck Hards <chuck.hards@gmail.com> wrote:
On 9/6/11, Chuck Hards <chuck.hards@gmail.com> wrote:
On 9/6/11, Chuck Hards <chuck.hards@gmail.com> wrote:
If you want to make a small, dedicated white-light solar scope, you can install the filter material JUST behind the objective.
OK, before someone else posts it, it works for Gregorians too.
Around and ahead of the optical surface of the secondary, but inside the tube itself.
My understanding is that Baader is coated on both sides, traditional mylar is just coated on one side. I think you are right Baader is the way to go, if you do not wish to spend a few dollars more for a glass filter, or if the color is important.
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.
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It does seem there are many grades of mylar films, some good for solar viewing some not so much and perhaps not even all that safe.
On 9/6/11, erikhansen@thebluezone.net <erikhansen@thebluezone.net> wrote:
My understanding is that Baader is coated on both sides,
I didn't remember that, but it makes sense. I'll look over the tech sheets when I get home. Thanks Erik!
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