Re: [APML]: Image Registration

["Michael Stecker" <mstecker@earthlink.net>]

The Astro-Photography Mailing List
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-----Original Message-----
From: Chuck Vaughn <aa6g@aa6g.org>
To: astro-photo@nightsky.com <astro-photo@nightsky.com>
Date: Wednesday, September 23, 1998 3:33 PM
Subject: Re: [APML]: Image Registration


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Chuck:
     I have not done tricolor for some years now, but know that others
sometimes have to use Photoshop in order to register difficult photos.  As I
understand from James Foster, he uses the Layers -- Transform -- Distort
command.  This allows for better alignment because of the problems of
chromatic aberration, field curvature and the many problems Jerry talked
about.  Also I think you will have far less trouble if you use a reflector
instead of your refractor for tricolor.  I initially tried tricolor with my
5" inch refractor, but gave up on the method because of the chromatic
aberration and registration problems.  There are ways around this  (Distort
and blue star treatment), but they are difficult to do and as long as PPF is
around, I do not think they are worth the effort. An exception would be for
those unusual conditions where color film does not work very well (e.g.
S-147).
     I must be lucky because I have had no image registration problems with
Picture Window when stacking my color negatives.  If you need help with your
tricolor work, I suggest you contact James Foster or Bill Fletcher.  They
have known about this problem for years and and should know how to deal with
it.

                             Michael Stecker