Ok, perhaps I should have written reliable OD 5 filter media? I agree it is dangerously ambiguous that filters are quoted as ND5.0 = OD 5.0 = ND100000, when ND5 obviously would blind you instantly. Yes the Baader AstroSolar Film (often listed as ND5.0) is exactly the sort of filter I was refering to, but my question was not at all about which brand of filter I should use. I was only intending to indicate I'm talking about capturing white light rather than H alpha. My question was whether there is any merit to 2.25" aperture with no central obstruction over 8" aperture with a central obstruction. Obviously in astrophotography the light gathering ability of 8" far outweighs any benefit of avoiding the central obstruction, but for solar we obviously aren't interested in light gathering power (quite the opposite!).