Re: [APML] Flat Fields for vignetting

[Steve.Holak@bcitpa.com]

Frank,

There was an article in Sky & Telescope last year on removing vignetting
and skyglow in Photoshop, by making a copy, erasing all the bright stars
and objects with the rubber-stamp tool, applying a Gaussian blur, and
subtracting that image from a copy of the original--it works similar to a
flat frame, and it works for photos or CCD.

Article: Astro Imaging ? Fixing Vignetting in Astrophotos
     By Sean Walker | September 2001,  p. 116-120

You can search  S & T archives and download the article (for a fee) , if
you don't have a subscription.

HTH

Steve Holak
Senior Software Architect

Brokerage Concepts IS Dept.
610-491-4879

email:  steve.holak@bcitpa.com


                                                                                                                      
                    "Frank Barrett"                                                                                   
                    <frankb02@bellso        To:     <astro-photo@seds.org>                                            
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                    Sent by:                Subject:     [APML] Flat Fields for vignetting                            
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                    11/15/2002 11:38                                                                                  
                    AM                                                                                                
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Hello list.  The last couple of rolls of film  I've shot using the Meade
f/6.3 focal reducer.  It does a great job, but  with my el cheapo OAG I
consistently get vignetting on longer exposures.   I've managed in
photoshop to remove this via Matt BenDaniels AV layer technique  (thanks
Matt) and via cropping, but I was wondering if it were possible to apply
flat field techniques like the CCD guys do.  Anyone doing this successfully
or is this just another one of my trojan horse ideas?  What are the best
ways to remove a consistent vignette pattern?  Thanks in  advance.


Carpe Noctem,  Frank

Astropix:  http://bellsouthpwp.net/f/r/frankb02/astropix.html





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