You're right, Erik, there is no reason that the scope shouldn't work well for any extremely narrowband application such as solar H-a viewing. It should work fine with an O3 or H-beta filter as well, though the aperture is probably too small for any but the brightest objects. Alas, the focuser must be used for the F/20 version. I lathe-turned the base to fit the 2" tubing and don't want to have to purchase and machine a second one. It's the Sky Instruments 1.25" all-aluminum refractor focuser and I added some "mag wheel" focuser knobs that I had on-hand. In practice, the tube is too long to be practical. Were I to make a serious H-a scope with a long-focus lens, I'd probably fold the optical path with a pair of mirrors. It would be much more stable on an equatorial mount in a folded configuration. I'll send you the photos privately since it appears that the gallery still isn't up. On 8/26/07, erikhansen@thebluezone.net <erikhansen@thebluezone.net> wrote:
Chuck,
The scope I put together for SLAS's H-Alpha DayStar filter is a 50 MM f 30, works good. Vaughan Parsons made a 80mm f 30 for his Daystar filter works very well, all singlets. The filter works well on anything longer than f 30, you should try it out on your singlet lens.