Re: [APML] Bill Fletcher's Tri-color work(was 23a filter)

["Brian and Leau Larmay" <brileau@earthlink.net>]

You know, I brought up the same topic once about tri- color vs. your average
color astro film on the deja astronomy NG and got knocked around as to the
method being to much work and not worth it.

Personally I dont get why its any harder, in fact, I want to try it once to
see what it is like also.
Tech Pan...thats a really fast film right?
How fast is fast?
Would the standard red, green, blue filters work by Cokin, or do they have
to be a certain kind of RGB filters?


Brian



----- Original Message -----
From: Ulrich Beinert <analemma@gmx.de>
To: <astro-photo@seds.org>
Sent: Thursday, June 15, 2000 6:28 AM
Subject: Re: [APML] Bill Fletcher's Tri-color work(was 23a filter)


>
> > Hello Scott:
> >       We all owe a lot to Bill Fletcher.  He was a pioneer in
> > film-digital astrophotography (not just tricolor).   I believe he
> > perfected his process in 1992 or perhaps 1993, which was years before
> > anyone on this list was doing such work.  He did this with Photoshop 2.5
> > (no layers) which made it vastly more difficult than it is today.  He
> > spoke to Adobe and they thought his process at the time was impossible.
> > Even with this discouragement he was able to develop a process that
works
> > quite well.  In the November, 1994 Sky and Telescope on page 98 he wrote
> > an article on his technique.  The article was general and gave little
> > specific data.  The lead photo of the article was a tricolor of
> > Antares-Rho Ophiuchus region which I took with my Tamron 180 mm f/2.5
> > lens and hypered Tech Pan film and Bill processed in Photoshop 2.5.  It
> > has been a long time since I took that photo (I think it was in 1993).
I
> > believe I used a Kodak 25A for the red, 58 for the green and 47 for the
> > blue.  The exposure times were 42 minutes in red, 80 minutes in green
and
> > 100 minutes in blue.  In later work I increased the green and the blue
> > exposures.  In my experience the hypered Tech Pan is least sensitive to
> > green light.  The most challenging tricolor I have done was of the very
> > dim SNR Simeis-147.
>
>
> If I understand this right, you take one photo through a red filter, one
> through green, and another through blue? Then what - stack them in
Photoshop
> assigning them to the red, green and blue channels, respectively, to get a
> color image? This sounds interesting; I want to try it....
>
> Ulrich
>
>
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