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68557Re: ngc 925 with a c14

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  • randy_nulman
    Jan 1, 2011
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      Hi Marc,

      It sounds like you are (correctly) using the L-LRGB method. I assume you flattened after the first step? If so, take that flattened image and boost the color saturation a reasonable amount via the steps I described earlier. This should increase color without increasing color noise.

      Then do the second luminance layering at whatever opacity level that maintains a combination of detail and color.

      Hope this makes sense and Happy New Year!

      Randy

      --- In ccd-newastro@yahoogroups.com, "marcjousset" <mj.astro@...> wrote:
      >
      > Hi Randy,
      >
      > Many thanks for your suggestions. My usual processing is to do first a combine with an opacity of 25% for the L layer. Then I boost the saturation (50-60%) of the result and blur it with a gaussian filter (3-4 pixels). Afterwards, I make a new combine with the L layer with an opacity of 100%. As you're suggesting, I could reduce this opacity a bit to boost the saturation...
      >
      > Regards,
      >
      > marc
      >
      > --- In ccd-newastro@yahoogroups.com, "randy_nulman" <rj.nulman@> wrote:
      > >
      > > Hi Marc,
      > >
      > > I know what it's like to have limited data, so may I make the following suggestions:
      > >
      > > First, boost the color saturation via "saturation" PS tools if working in RGB space, or the a and b channel (contrast) if working in LAB space. Don't try to do it using the histogram levels technique if your data is weak.
      > >
      > > Also, you do have some nice detail from the luminance already. Thus another idea is to control the opacitity of the luminance layer when doing the LRGB combine (maybe to around 70%)? Then you still maintain most of your detail and the color will be stronger.
      > >
      > > Just some thoughts...
      > >
      > > Regards,
      > > Randy
      > > http://nulman.darkhorizons.org
      > >
      > >
      > > --- In ccd-newastro@yahoogroups.com, "marcjousset" <mj.astro@> wrote:
      > > >
      > > > Hi Randy,
      > > >
      > > > Unfortunately, I was not able to get more RGB during the night. As a result, the SNR in the RGB raw image is really poor. It is one of my main problem from my polluted backyard (SQM 19,5). With more images, I certainly could push a bit the saturation in the faintest area. Each time, I favour the L images but I am mistaken. Next time, I have to catch more individual color images...
      > > >
      > > > Happy holidays,
      > > >
      > > > Marc
      > > >
      > > >
      > > > --- In ccd-newastro@yahoogroups.com, "randy_nulman" <rj.nulman@> wrote:
      > > > >
      > > > > Hi Marc,
      > > > > I think you also have some great detail in your image...my only concern was the color saturation. This is a processing decision, not necessarily equipment or seeing related...nothing is right or wrong with either decisions...
      > > > >
      > > > > Happy Holidays,
      > > > > Randy
      > > > > http://nulman.darkhorizons.org
      > > > >
      > > > > --- In ccd-newastro@yahoogroups.com, "marcjousset" <mj.astro@> wrote:
      > > > > >
      > > > > > Hi Randy,
      > > > > >
      > > > > > Thanks for your comment. I have seen your image again an again before posting mine. Yours is really a great image, with so much details and beautiful colors. This being so, a C14 is not a 20" RC...
      > > > > > I think that the main differences are the diameter, the focal lenth and the optical formula. A RC is able to give sharper stars than a SCT.
      > > > > >
      > > > > > Best regards,
      > > > > >
      > > > > > Marc
      > > > > >
      > > > > >
      > > > > > --- In ccd-newastro@yahoogroups.com, "randy_nulman" <rj.nulman@> wrote:
      > > > > > >
      > > > > > > Hi Marc,
      > > > > > >
      > > > > > > Very nice! I saw the comments about potentially too much blurring/noise reduction, but don't totally agree. I think this is quite nice but maybe lacking in color saturation? Here's my older version for comparison:
      > > > > > >
      > > > > > > http://www.nulman.darkhorizons.org/images/ngc925.html
      > > > > > >
      > > > > > > This was taken with the 20" RC in NM (4220mm FL). I think you brought out similar detail (seeing conditions for my image were not great those nights), but the color saturation seems to make the difference?
      > > > > > >
      > > > > > > Let me know what you think,
      > > > > > >
      > > > > > > Regards,
      > > > > > > Randy
      > > > > > > http:nulman.darkhorizons.org
      > > > > > >
      > > > > > >
      > > > > > > --- In ccd-newastro@yahoogroups.com, "marcjousset" <mj.astro@> wrote:
      > > > > > > >
      > > > > > > > Hi all,
      > > > > > > >
      > > > > > > > I would like to share my lastest image of ngc925 taken with my "old" C14. This
      > > > > > > > one has been acquired in mi october during a night of poor seeing. The FWHM on the raw files is about 2,4 to 2,8".
      > > > > > > >
      > > > > > > > http://www.astrosurf.com/jousset/forums/ngc925_101011.jpg
      > > > > > > >
      > > > > > > > C14 at f/8,4
      > > > > > > > STL4020 + AOL
      > > > > > > > L : 25x10min
      > > > > > > > RGB : 5x5 min
      > > > > > > >
      > > > > > > > One could find a version reduced to 75% on my website.
      > > > > > > >
      > > > > > > > Happy Christmas to all.
      > > > > > > >
      > > > > > > > Marc
      > > > > > > > http://www.astrosurf.com/jousset
      > > > > > > >
      > > > > > >
      > > > > >
      > > > >
      > > >
      > >
      >
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