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Re: Stars and coma aberration

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  • Carl von Einem
    ... This might work in a similar way with a masking technique in Photoshop (or GIMP). Take your already shot (focused) image of the sky, on a copied layer
    Message 1 of 5 , Sep 17, 2013
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      > Posted by: "Erik Krause" on Mon Sep 16, 2013 10:39 am ((PDT))
      >
      > Am 14.09.2013 01:36, schrieb panovrx:
      >> One peculiarity about star photos is that with modern cameras you can
      >> easily record lots of stars but the brightest stars, the ones that we
      >> recognize as the constellations, get lost in the myriads of stars.
      >> Ideally there would be a filter that thins out the faintest stars
      >> without dimming the nebulosities.
      >
      > Slight defocus can help to see the constellations clearer. This way
      > bright stars appear larger while faint ones get invisible. A sharp image
      > can be done in a second step to get the faint stars and the terrestrial
      > subjects.

      This might work in a similar way with a masking technique in Photoshop
      (or GIMP). Take your already shot (focused) image of the sky, on a
      copied layer apply a Gaussian blur (start with a small value like 0.5)
      and after that compress the levels (Cmd+L in Photoshop) for that layer.
      Set layer to brighten only.

      Carl
    • Erik Krause
      ... This might have some effect, but not the same like defocus when shooting. The reason is that bright stars get overexposed soon. Since they are a single
      Message 2 of 5 , Sep 17, 2013
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        Am 17.09.2013 13:06, schrieb Carl von Einem:
        >> >Slight defocus can help to see the constellations clearer. This way
        >> >bright stars appear larger while faint ones get invisible. A sharp image
        >> >can be done in a second step to get the faint stars and the terrestrial
        >> >subjects.
        > This might work in a similar way with a masking technique in Photoshop
        > (or GIMP). Take your already shot (focused) image of the sky, on a
        > copied layer apply a Gaussian blur (start with a small value like 0.5)
        > and after that compress the levels (Cmd+L in Photoshop) for that layer.
        > Set layer to brighten only.

        This might have some effect, but not the same like defocus when
        shooting. The reason is that bright stars get overexposed soon. Since
        they are a single point when focused correctly they get and stay white.
        If defocused the light is distributed across several pixels which aren't
        overexposed that fast. This way you might even discover, that stars are
        actually colored (like I did years ago when shooting the night sky over
        altiplano in Peru - one of the regions with least light pollution in the
        world BTW).

        --
        Erik Krause
        http://www.erik-krause.de
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