Again, you are throwing a lot of light away with a Herschel wedge, so even if the filter was narrow enough to fully screen out the off-band light, you probably would not see anything. Imaging with long exposures with the Herschel wedge and the nighttime "nebula" H-alpha filters would only show white-light detail because these filters are just plain far too broad to kill off enough of the light from the photosphere to let you see much of the chromosphere. The narrowest I know of are the Baader H-alpha CCD with a Full-width at Half Maxima of 65 angstroms and the Custom Scientific H-alpha filter with a FWHM of about 41 Angstroms. Now it *might* be possible with an occulting disk to image the brightest prominences with these two filters at a good high-altitude site, but I would not risk it visually. Even the older Baader Coronagraph used an 11 Angstrom passband filter along with occulting disks. To see prominences alone without the use of an occulting disk requires a bandwidth that is about 1.5 angstroms or narrower (as is found with the fine Thousand Oaks prominence filters). Seeing H-alpha chromospheric disk detail requires a bandwidth of under one angstrom, so the H-alpha nebula filters just are way too broad to work for solar use. People who try the night H-alpha filters with regular white-light solar filters will just see a pretty dim red sun with more or less the same features that are seen with the white light filter alone. Again, for the lowest entry cost in solar H-alpha viewing, the Coronado PST is probably the best way to go. Clear skies to you.