Re: [APML] Stacking Software

[Jose Miguel Benito Huete <jbenito1@teleline.es>]

Jerry,
Maybe I am not doing things right, but when I use registar the images get combined
in registar and I don't need Photoshop for this. I only use Photoshop for color
balance, etc.. When I register two color images, I get a B&W registered image and
then I go to the combine command to get the final color image that is the
combination of the two originals. Regarding the sky fog limit, do you know the
limit for an f:6 optical system using Elitechrome 200 slide film?
Thanks
Jose Miguel

Jerry Lodriguss escribió:

> At 12:05 AM 9/26/2002 -0400, you wrote:
> >I am using Registar and I agree with Jerry. It is wondeful. After having said
> >this I have some quetions about the stacking proccess. I had the idea that
> >when you stack two or more images of the same object, the signal you have in
> >the final composite is the sum of the signals from the original images,
> >whereas the background is not the sum but something like an average. But after
> >having used Registar for a while I have discovered that the "only" advantage
> >of stacking is that the final image have less background but no more signal.
> >So it is not the same a stack of two frames exposed half an hour each, that a
> >single frma exposed for an hour. The stack of the two frmaes may have less
> >backgound but the one hour single frma will have more signal. In conclusion
> >the stacking proccess using programs such as Registar is not the panacea to
> >obtain great images by simply adding a lot of underexpossed frames to get a
> >beautifully color saturated, high contrast final composite. So my questions
> >are: 1) Is there a balanced solution to get the maximum capabilities of the
> >stacking proccess?:2) Is the diminishing of the backgound the only advantage
> >of stacking several images?
>
> You have it right.  Film is not CCD, and adding together 100 one minute
> exposures do not add up to 1 one hundred minute exposure.
>
> After you register the images in Registar, there are different ways of
> combining them in Photoshop to boost the signal. See:
>
> http://www.astropix.com/HTML/J_DIGIT/COMPEXP2.HTM
>
> Some methods boost the signal while keeping the sky background noise the
> same. Others produce the exact equivalent of an average, which keeps the
> signal the same while reducing the sky background noise.
>
> The answer to both of your questions, for film at least, is basically the
> same. Shooting multiple originals, each to the skyfog limit, and averaging
> them produces a great benefit in reducing the background noise, which then
> lets you boost the signal with a levels or curves adjustment.
>
> Jerry
>
> Astronomical photography: http://www.astropix.com
>
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