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M51 - Whirlpool Galaxy

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  • Jeff Armstrong
    The Whirlpool Galaxy (also known as Messier 51a, M51a, or NGC 5194) is an interacting grand-design spiral galaxy in the constellation Canes Venatici.  The
    Message 1 of 4 , May 15, 2013
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      The Whirlpool Galaxy (also known as Messier 51a, M51a, or NGC 5194) is an
      interacting grand-design spiral galaxy in the constellation Canes Venatici. 


      The subs for this image are the longest I've used to date.  20min for RGB and
      30min for Ha.

      I had to do some cropping as I made the mistake of centering the image on the
      companion galaxy NGC 5195 during acquisition.  This offset M51 more than I
      liked. 

      http://astrob.in/42126/

      Jeff Armstrong

      [Non-text portions of this message have been removed]
    • Bernard Miller
      Jeff, Very nice detail. On my monitor it looks like there is a green tint to the image. You may want to try the HLVG filter.
      Message 2 of 4 , May 16, 2013
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        Jeff,



        Very nice detail. On my monitor it looks like there is a green tint to the
        image. You may want to try the HLVG filter.



        http://www.deepskycolors.com/archivo/2010/04/26/hasta-La-Vista-green.html



        Bernard





        From: ccd-newastro@yahoogroups.com [mailto:ccd-newastro@yahoogroups.com] On
        Behalf Of Jeff Armstrong
        Sent: Wednesday, May 15, 2013 2:31 PM
        To: ccd-newastro@yahoogroups.com; CelestronCGEM@yahoogroups.com;
        starlightxpress@yahoogroups.com
        Subject: [ccd-newastro] M51 - Whirlpool Galaxy





        The Whirlpool Galaxy (also known as Messier 51a, M51a, or NGC 5194) is an
        interacting grand-design spiral galaxy in the constellation Canes Venatici.


        The subs for this image are the longest I've used to date. 20min for RGB
        and
        30min for Ha.

        I had to do some cropping as I made the mistake of centering the image on
        the
        companion galaxy NGC 5195 during acquisition. This offset M51 more than I
        liked.

        http://astrob.in/42126/

        Jeff Armstrong

        [Non-text portions of this message have been removed]





        [Non-text portions of this message have been removed]
      • Stan
        ... You don t have to rely on appearance to determine color hues. Measure the color ADU differentials. A CCDStack measurement of an area near the satellite
        Message 3 of 4 , May 17, 2013
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          --- "Bernard Miller" <bgmiller011@...> wrote:
          > On my monitor it looks like there is a green tint

          You don't have to rely on appearance to determine color hues.
          Measure the color ADU differentials.
          A CCDStack measurement of an area near the satellite yields:

          R:G:B ratio 1.01 : 1.03 : 0.96

          So it is definitely greenish, which is an unnatural hue if the intent was to produce solar system based colors. Perhaps the sky background was mishandled (a common cause of differential greening).

          Stan
        • Bob Franke
          Using six SDSS-DR7 stars, eXcalibrator gives an RGB correction of 1.00, 0.99 and 1.07. This adjustment sets the area, that Stan mentioned, very close to a
          Message 4 of 4 , May 17, 2013
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            Using six SDSS-DR7 stars, eXcalibrator gives an RGB correction of 1.00, 0.99 and 1.07. This adjustment sets the area, that Stan mentioned, very close to a neutral gray.

            Cheers,
            Bob


            --- In ccd-newastro@yahoogroups.com, "Bernard Miller" <bgmiller011@...> wrote:
            >
            > Jeff,
            >
            >
            >
            > Very nice detail. On my monitor it looks like there is a green tint to the
            > image. You may want to try the HLVG filter.
            >
            >
            >
            > http://www.deepskycolors.com/archivo/2010/04/26/hasta-La-Vista-green.html
            >
            >
            >
            > Bernard
            >
            >
            >
            >
            >
            > From: ccd-newastro@yahoogroups.com [mailto:ccd-newastro@yahoogroups.com] On
            > Behalf Of Jeff Armstrong
            > Sent: Wednesday, May 15, 2013 2:31 PM
            > To: ccd-newastro@yahoogroups.com; CelestronCGEM@yahoogroups.com;
            > starlightxpress@yahoogroups.com
            > Subject: [ccd-newastro] M51 - Whirlpool Galaxy
            >
            >
            >
            >
            >
            > The Whirlpool Galaxy (also known as Messier 51a, M51a, or NGC 5194) is an
            > interacting grand-design spiral galaxy in the constellation Canes Venatici.
            >
            >
            > The subs for this image are the longest I've used to date. 20min for RGB
            > and
            > 30min for Ha.
            >
            > I had to do some cropping as I made the mistake of centering the image on
            > the
            > companion galaxy NGC 5195 during acquisition. This offset M51 more than I
            > liked.
            >
            > http://astrob.in/42126/
            >
            > Jeff Armstrong
            >
            > [Non-text portions of this message have been removed]
            >
            >
            >
            >
            >
            > [Non-text portions of this message have been removed]
            >
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