Re: [APML] H-A filters

["Richard Crisp" <rdcrisp@earthlink.net>]

----- Original Message -----
From: "Gene Horr" <genehorr@houston.rr.com>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Wednesday, December 31, 2003 6:48 AM
Subject: RE: [APML] H-A filters


> -----Original Message-----
> From: astro-photo-bounces@seds.org
> [mailto:astro-photo-bounces@seds.org]On Behalf Of John C. Mirtle
>
> > Gene,
> >     I don't think it was designed as a visual filter. It was sold and
> > marketed as an astrophoto filter, for use with tech pan.
>
> Aha.  Thanks for the information.


Halpha is a tough wavelength to see visually. The eye is just too responsive
to deep red light in my experience. If you want to use it for visual, I
suggest using Hbeta as it is much closer to the peak sensitivity of the eye,
and usually when I see Halpha, I also see Hbeta in the same shape of the
same object.

In fact I sort of view Hbeta as being a "visual Halpha" filter. I am
confident the physicists out there will have a problem with that concept,
but it seems pretty well on-target from a practical perspective.

rdc

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