Quote:
Originally Posted by Tinderboxsky
I would not make a 12" filter. The image will be too bright to look at comfortably. Even 8" ones are overly bright. In your case I would be making an off axis 4 to 5 inch filter. This is all the aperture you need for the Sun and will deliver an excellent, comfortable image. You will also have the advantage of no central obstruction. In any event the standard sheets would not cover 12".
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You can buy Thousand Oaks solar film (gives a natural orange image) on eBay in sheets up to 12" x 12" for about $45 (including postage). The biggest full-aperture filter I have made is for my 200 mm SCT, and it is very comfortable for viewing the Sun. (And I made a couple of smaller filters for my finderscope, binoculars and a 90 mm Mak with the corner off-cuts.)
But yes, I agree that a 5" off-axis filter would be fine (and cheaper).