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Re: NGC2903 Barred Spiral Galaxy in Leo

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  • Stan
    ... Pretty good image. If you are posting it here for some critique and advice then read on. If not then please stop reading. The color balance is incorrect as
    Message 1 of 5 , Feb 23, 2013
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      --- "jeffreyjongmans" <jeffreyjongmans@...> wrote:
      > NGC2903 with a 10" RC on a DDM60 with a QSI 683wsg-8
      > http://jeffreyjongmans.nl/photo.php?id=29

      Pretty good image.
      If you are posting it here for some critique and advice then read on.
      If not then please stop reading.

      The color balance is incorrect as witnessed by the many green stars. Green is an impossible star color according to the blackbody thermal spectrum and human perceived color. Otherwise our Sun would be green, which it actually is but human eye/mind does not perceive it that way. The error could be a mistake in handling the color distortions introduced by light pollution (color contamination of sky pollution cannot be balanced out using color ratios; it is necessary to do offset normalization).

      The Lum is much underexposed with poor S/N and shallow depth. Some of that is due to light pollution but it is really due to insufficient total Lum exp time. Good LRGB imaging of galaxies takes an enormous amount of time (often at least 5 nights of data acquisition and often much more). It seems that many people settle for an insufficient Lum so as to produce the mandatory color image (as dictated by the "color mafia" <g>). Personally I would much rather see an interesting well defined and deep grayscale image than pretty color splotches.

      To me the display image is overly large, enveloping the galaxy in a useless and uninteresting star field. If the exposure was considerably deeper then the surrounding field might have some interesting distant galaxies, but it isn't and doesn't. This is a very common large-camera syndrome and I'm sure it is born of a desire to exploit the full size of an expensive CCD, no doubt accompanied by the sentiment that it provides aesthetic framing.

      I realize that these words might seem harsh and apologize in advance if I over presumed.

      Stan
    • jeffreyjongmans
      Hi Stan, Thank you for this explanation! I was posting it to get some critique... :) This image was shot with a half lit Moon and heavy light polluted sky, I
      Message 2 of 5 , Feb 24, 2013
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        Hi Stan,

        Thank you for this explanation! I was posting it to get some critique... :)
        This image was shot with a half lit Moon and heavy light polluted sky, I live in the Netherlands, that's the worst place on Earth for AP. I don't get many clear nights...

        Cheers,

        JJ

        --- In ccd-newastro@yahoogroups.com, "Stan" <stan_ccd@...> wrote:
        >
        > --- "jeffreyjongmans" <jeffreyjongmans@> wrote:
        > > NGC2903 with a 10" RC on a DDM60 with a QSI 683wsg-8
        > > http://jeffreyjongmans.nl/photo.php?id=29
        >
        > Pretty good image.
        > If you are posting it here for some critique and advice then read on.
        > If not then please stop reading.
        >
        > The color balance is incorrect as witnessed by the many green stars. Green is an impossible star color according to the blackbody thermal spectrum and human perceived color. Otherwise our Sun would be green, which it actually is but human eye/mind does not perceive it that way. The error could be a mistake in handling the color distortions introduced by light pollution (color contamination of sky pollution cannot be balanced out using color ratios; it is necessary to do offset normalization).
        >
        > The Lum is much underexposed with poor S/N and shallow depth. Some of that is due to light pollution but it is really due to insufficient total Lum exp time. Good LRGB imaging of galaxies takes an enormous amount of time (often at least 5 nights of data acquisition and often much more). It seems that many people settle for an insufficient Lum so as to produce the mandatory color image (as dictated by the "color mafia" <g>). Personally I would much rather see an interesting well defined and deep grayscale image than pretty color splotches.
        >
        > To me the display image is overly large, enveloping the galaxy in a useless and uninteresting star field. If the exposure was considerably deeper then the surrounding field might have some interesting distant galaxies, but it isn't and doesn't. This is a very common large-camera syndrome and I'm sure it is born of a desire to exploit the full size of an expensive CCD, no doubt accompanied by the sentiment that it provides aesthetic framing.
        >
        > I realize that these words might seem harsh and apologize in advance if I over presumed.
        >
        > Stan
        >
      • Stan
        ... Then I take it all back and congratulate you for an amazing image in the face of adversity!! Stan
        Message 3 of 5 , Feb 25, 2013
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          --- "jeffreyjongmans" <jeffreyjongmans@...> wrote:
          > This image was shot with a half lit Moon and heavy light
          > polluted sky, I live in the Netherlands,
          > that's the worst place on Earth for AP...

          Then I take it all back and congratulate you for an amazing image in the face of adversity!!

          Stan
        • Hemant Hariyani
          Hello Jeffrey, That is a beautiful image. Very nice details and color balance. Regards Hemant On Thu, Feb 21, 2013 at 3:52 PM, jeffreyjongmans
          Message 4 of 5 , Feb 26, 2013
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            Hello Jeffrey,

            That is a beautiful image. Very nice details and color balance.

            Regards
            Hemant


            On Thu, Feb 21, 2013 at 3:52 PM, jeffreyjongmans <
            jeffreyjongmans@...> wrote:

            > **
            >
            >
            > From a light polluted backyard (including Moonlight) in the Netherlands;
            > beautiful little galaxy NGC2903 in Leo.
            > NGC2903 with a 10" RC on a DDM60 with a QSI 683wsg-8
            > http://jeffreyjongmans.nl/photo.php?id=29>
            >
            > [Non-text portions of this message have been removed]
            >
            >
            >


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