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Re: Stars and coma aberration

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  • 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 1 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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