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Thread: Preprocessing artifacts

  1. #1
    Junior Member
    Join Date
    Aug 2017
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    Preprocessing artifacts

    i've noticed repeatedly after preprocessing the resultant image looks like the pixel arrangement is always diagonal from bottom left to top right - see attachment
    Click image for larger version. 

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    Is this a result of the stacking algorithm and should I be worried?

  2. #2
    Junior Member
    Join Date
    Aug 2017
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    No one...not even Fabio?

  3. #3
    Developer
    Join Date
    Apr 2012
    Posts
    461
    Hello, I missed the message.
    The cause seems to me an imperfect dark frame correction, which gets a diagonal shape cause the auto-alignment of several images. If you orient the camera with the equatorial axes the noise should get a horizontal shape.
    Remember that the master dark frame must be at least the average of 4 frames (8 or more is better).
    If you are using a bias as a dark frame, then again you should average several frames.
    The image also seems extremely oversampled: you may work in binning 2x2 without losing any information.
    Greetings,
    Fabio.

  4. #4
    Member
    Join Date
    May 2012
    Location
    Monterey county Ca.
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    78
    Here is a photo from a book about astro photography by Ron Wodaski that shows similar artifacts due to stacking very short sub exposures!

    Click image for larger version. 

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    Iver

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