[frolinmod]

You'd need a sub-angstrom Ha filter. Your typical CCD imaging narrow band Ha filter is 30 to 50 angstroms (3nm to 5nm) wide. That is far too wide to see prominences.

For white light solar viewing I'm currently using a Lunt Herschel wedge with a Baader solar continuum filter and a Lunt zoom eyepiece. The Baader solar continuum filter is a 10nm wide filter centered around 540nm in the green. I can put the Herschel wedge on the back of any refractor, preferably an an APO or semi-APO. I currently have it on a Stellarvue 80ED with a moonlite focuser. Note sure what it would look like to replace the solar continuum filter with an Ha filter. Probably not much. I don't have a 1.25-inch or 2-inch mounted Ha filter to try. But I suspect it would just act like a very deep red filter.