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71842Re: q. about images without flats

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  • Stan
    Oct 1 9:25 AM
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      --- "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.

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