While various line filters, narrowband filters and color filters can increase contrast when used behind a white light solar filter, none of them are narrow enough (afaik) to show proms or other Ha features.
Ha scopes work at less than 1 angstrom; 12nm = 120 angstroms.
Edit: google tells me that up to 10nm can be useful for proms, though with reduced contrast, so it might be a matter for experimentation.
Last edited by casstony; 19-12-2011 at 12:02 PM.
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