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Old 09-04-2013, 06:53 PM
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Geoff45 (Geoff)
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Join Date: Jul 2006
Location: Sydney
Posts: 2,412
Reflection from the glass cover of the ccd chip back up to the filter, then reflected back down onto the chip is the most common cause. Less common are dew on the OG, high thin cloud, dirty optics. Here is a comprehensive article http://www.astrodon.com/articles_faq...ase:391,355,49
Geoff
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