Re: [APML] Astrophotography 2004 - Price Shock Horror

["Stuart Heggie" <stuart.j.heggie@sympatico.ca>]

Richard, thanks for the correction. By the way, my comment was meant as a compliment - I think your
stuff is great, just way beyond my skills so my intent was to say that I can be wow'd by your stuff
but still take pleasure in my modest beginner's efforts knowing that I'm just on a much earlier
part of the learning curve. Hope I didn't offend.

Stuart
http://www3.sympatico.ca/stuart.j.heggie/Stuart.J.Heggie/
Flesherton, Ontario, Canada

----- Original Message -----
From: "Richard Crisp" <rdcrisp@earthlink.net>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Wednesday, June 02, 2004 10:27 PM
Subject: Re: [APML] Astrophotography 2004 - Price Shock Horror


>
> ----- Original Message -----
> From: "Stuart Heggie" <stuart.j.heggie@sympatico.ca>
>
> > That is so cool. Just different from film. When Richard Crisp posts one of
> his exotic line filter
> > shots of an obscure galaxy I just marvel but I don't feel lessened by it
> because I've got an old
>
> No problem making the comment Stuart, but for the record, I use the emission
> line filters on *nebulae* usually. Galaxies, except for the close ones with
> lots of HII action, aren't very good targets for emission line imaging
> except:
>
> Turns out that if you are about 450MLY away that a Hydrogen Alpha line will
> redshift to about the same wavelength as [SII] at rest: the 656.3nm Ha line
> becomes about 674nm which means in theory you could look for Ha activity in
> a 450MLY away galaxy (usually seen in spirals) using an [SII] filter. For
> continuum subtraction, you could use a 10nm wide Ha filter with a 3nm wide
> [SII] filter because nothing seems to shift into the slot occupied by Ha.
>
> Nits, twits, and details. Sorry to bore you all....
>
> rdc
>
>
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