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71844Re: q. about images without flats

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  • CurtisC
    Oct 1, 2012
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      There was no flat-fielding. That's the point of showing the image.

      --- In ccd-newastro@yahoogroups.com, "Stan" <stan_ccd@...> wrote:
      >
      > --- "CurtisC" <calypte@> wrote:
      > > The corners, where illumination is weakest, are *lighter*
      >
      > That can be due to incorrect flat fielding but if it is in the raw image then it is probably from a light leak. "Sky flooding" is where the camera is exposed to light rays directly from the sky. Sky flooding is usually brighter further off-axis.
      >
      > A Mak-Cass with a small secondary will produce sky flooding. I once had an f/14 Mak-Cass with such a small secondary that it also came with a set of obstruction rings to enlarge the secondary shhadow to prevent sky flooding.
      >
      > Stan
      >
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