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The big difference between Daystar and, well, everyone else, is Daystar need the wavefront to be (nearly) parallel, and this can only be achieved at high F-ratios
Hence before you know it, you are looking at some pretty narrow fields...i.e. way less that a full solar disk.
I've played with almost all H-alpha filters/scopes on the market, IMHO front mounted etalons do the best job in terms of even field illumination. (wavefronts from Sol are about as parallel as they can get at the objective end).
With a front mounted etalon you can use any focal length & f-ratio you want.
The rub is they cost more.
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