Hi there. You posted:

Question: Back in the late 60s/early 70s S&T ran some articles on ATM
built H-alpha filters, that seemed to provide good results. The
technology was different than current commercial products, but
sub-angstrom imaging was claimed. Can anyone point me at current
home-built H-alpha filter information and/or web sites?


Well, AMATEUR TELESCOPE MAKING Book III (original edition) has some
information on such filters using optical activity in certain crystal
substances, but as I recall, it was very difficult to get the materials
and the bandwidths weren't quite as good as the filters which used
Fabry-Perot Etalons. The other method cited in Sky and Telescope was
the Spectrohelioscope, which is essentually a "scanning" spectroscope
set on the H-alpha line. It worked, but had a limited field of view.
One guy I saw at an Astronomical League convention had one, and I asked
him about it. He said that the DayStar filters like the one I had
worked better, but since the sky was cloudy, I was unable to judge for
myself. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

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