Re: [APML]: Image Registration

[Chuck Vaughn <aa6g@aa6g.org>]

The Astro-Photography Mailing List
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Jerry,

Just from the causes you've listed it seems unlikely that they can
all be controlled to the degree we'd like them to be. A better
alignment tool is probably the only answer.

If you or anyone else would like to wrestle with the images I've been,
I could upload the full res jpegs of Robert's green and blue Veil
exposures for you to try. These are the ultimate in bad. I had far
better luck aligning my blue and green Pelican refractor exposures
to my 500mm lens red Pelican exposure! I've never seen anything as
bizarre as these.

Chuck

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> Several things come to mind.
> 
> 1. Someone said that Jonathan Sacks discovered a problem with the
> registration engine in the current release version of PW.  I believe he
> correted it in one of the later "astro" non-public releases, maybe the one
> with the ADD function as an addition to the composite methods. Philip may
> know the answer to this.
> 
> 2. Film creep during the exposure.  I see this all the time on my negs shot
> under same conditions you mention above.
> 
> 3. Slight buckeling/warping of the film, different from frame to frame, in
> the film holder during scanning.
> 
> 4. Scanning irregularities, especially in scanners that move the film to
> scan. Try scanning the same neg twice in a row without touching anything
> and then see if you can perfectly align those two scans. Won't gain you
> anything s/n wise, but might reveal if it's a scanning problem.
> 
> 5. You're behind on your payments to the devil. <G>
> 
> Jerry
> mailto:jml@astropix.com
> Web page: http://www.astrosurf.com/astropix/index.html
> Astrophotography,Photoshop enhancement tips and techniques