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RE: [ccd-newastro] M5 MX7-C Colour image

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  • Ivor Barker
    Thats great Ray ! I just tweaked my tif file and uploaded it to the group. what a difference. Cant figure out the masking though. Cheers !! --Ivor ... -- Ivor
    Message 1 of 4 , May 4, 2001
      Thats great Ray !

      I just tweaked my tif file and uploaded it to the group. what a difference.
      Cant figure out the masking though.

      Cheers !!
      --Ivor
      At 12:23 PM 5/4/2001 -0700, you wrote:
      >That bright area on the left side is almost all on the blue image. You can
      >learn some interesting things about the color balance of your images by
      >examining the Levels histograms in Photoshop. It's a good idea to compare
      >the RGB, R, G, and B histograms to see how they line up with respect to each
      >other.
      >
      >Here is a link to an image that shows the four histograms for your globular
      >image:
      >
      >http://www.wodaski.com/wodaski/images/img/shoulder_comparison.jpg
      >
      >Note that the red and green histograms line up about the same. The red
      >arrows point to approximately the same height on the histogram curves. The
      >RGB histogram pushes out a little to the right of the R and G ones; the B
      >histogram shows why. The B image has many more pixels at the dim end of the
      >curve. This usually indicates either a light pollution gradient, or a
      >general high background level.
      >
      >To get a look at the blue channel, select it in the Channels palette, and
      >apply a very heavy brightening curve to it (just temporarily; don't click
      >OK). Notice how much brighter the left edge is. You can construct a
      >mask/selection, and then adjust Levels for just the blue channel to remove
      >the gradient.
      >
      >I would also suggest that you apply an overall brightening curve to the
      >image (Image | Adjust | Curves), as shown in this image:
      >
      >http://www.wodaski.com/wodaski/images/img/ivor_curve.jpg
      >
      >This boosts the lowest levels a lot, the mid levels a little, and the
      >brightest ones don't get much of a boost. This brings out more stars in the
      >globular:
      >
      >http://www.wodaski.com/wodaski/images/img/ivor_glob.jpg
      >
      >This is a lot like doing digital development in Maxim, but without the halos
      >around stars that result from the sharpening. I use this a lot to reveal
      >subtle detail, and then I can separately do unsharp masking, deconvolution,
      >etc. to control my sharpening exactly.
      >
      >Ron Wodaski
      >The New CCD Astronomy
      >http://www.newastro.com
      >
      >-----Original Message-----
      >From: Ivor Barker [mailto:ibarker@...]
      >Sent: Friday, May 04, 2001 9:32 AM
      >To: ccd-newastro@yahoogroups.com
      >Subject: [ccd-newastro] M5 MX7-C Colour image
      >
      >
      >http://www.employees.org/~ibarker/Astronomy/pages/m5.htm
      >
      >I think I have got the processing sorted now, although I still need to sort
      >out flat-field and dark extraction as I appear to have a bright area on the
      >left side.
      >
      >Cheers !!
      >--
      > Ivor Barker
      >AIM - rekrabrovi
      >10" LX 200, 10" Dob, ST-80, ST-237, MX7C
      >37 08 24 N 121 36 25 W
      >http://www.employees.org/~ibarker/Astronomy
      >
      >
      >To unsubscribe from this group, send an email to:
      >ccd-newastro-unsubscribe@egroups.com
      >
      >
      >
      >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
      >
      >
      >
      >To unsubscribe from this group, send an email to:
      >ccd-newastro-unsubscribe@egroups.com
      >
      >
      >
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      --
      Ivor Barker
      AIM - rekrabrovi
      10" LX 200, 10" Dob, ST-80, ST-237, MX7C
      37 08 24 N 121 36 25 W
      http://www.employees.org/~ibarker/Astronomy
    • Ivor Barker
      Sorry Ron, I just sent an email to Ray Gralak, got my Rons and Rays mixed up !
      Message 2 of 4 , May 4, 2001
        Sorry Ron, I just sent an email to Ray Gralak, got my Rons and Rays mixed up !
        :-)
        At 12:21 PM 5/4/2001 -0700, you wrote:
        >Thats great Ray !
        >
        >I just tweaked my tif file and uploaded it to the group. what a difference.
        >Cant figure out the masking though.
        >
        >Cheers !!
        >--Ivor
        >At 12:23 PM 5/4/2001 -0700, you wrote:
        >>That bright area on the left side is almost all on the blue image. You can
        >>learn some interesting things about the color balance of your images by
        >>examining the Levels histograms in Photoshop. It's a good idea to compare
        >>the RGB, R, G, and B histograms to see how they line up with respect to each
        >>other.
        >>
        >>Here is a link to an image that shows the four histograms for your globular
        >>image:
        >>
        >>http://www.wodaski.com/wodaski/images/img/shoulder_comparison.jpg
        >>
        >>Note that the red and green histograms line up about the same. The red
        >>arrows point to approximately the same height on the histogram curves. The
        >>RGB histogram pushes out a little to the right of the R and G ones; the B
        >>histogram shows why. The B image has many more pixels at the dim end of the
        >>curve. This usually indicates either a light pollution gradient, or a
        >>general high background level.
        >>
        >>To get a look at the blue channel, select it in the Channels palette, and
        >>apply a very heavy brightening curve to it (just temporarily; don't click
        >>OK). Notice how much brighter the left edge is. You can construct a
        >>mask/selection, and then adjust Levels for just the blue channel to remove
        >>the gradient.
        >>
        >>I would also suggest that you apply an overall brightening curve to the
        >>image (Image | Adjust | Curves), as shown in this image:
        >>
        >>http://www.wodaski.com/wodaski/images/img/ivor_curve.jpg
        >>
        >>This boosts the lowest levels a lot, the mid levels a little, and the
        >>brightest ones don't get much of a boost. This brings out more stars in the
        >>globular:
        >>
        >>http://www.wodaski.com/wodaski/images/img/ivor_glob.jpg
        >>
        >>This is a lot like doing digital development in Maxim, but without the halos
        >>around stars that result from the sharpening. I use this a lot to reveal
        >>subtle detail, and then I can separately do unsharp masking, deconvolution,
        >>etc. to control my sharpening exactly.
        >>
        >>Ron Wodaski
        >>The New CCD Astronomy
        >>http://www.newastro.com
        >>
        >>-----Original Message-----
        >>From: Ivor Barker [mailto:ibarker@...]
        >>Sent: Friday, May 04, 2001 9:32 AM
        >>To: ccd-newastro@yahoogroups.com
        >>Subject: [ccd-newastro] M5 MX7-C Colour image
        >>
        >>
        >>http://www.employees.org/~ibarker/Astronomy/pages/m5.htm
        >>
        >>I think I have got the processing sorted now, although I still need to sort
        >>out flat-field and dark extraction as I appear to have a bright area on the
        >>left side.
        >>
        >>Cheers !!
        >>--
        >> Ivor Barker
        >>AIM - rekrabrovi
        >>10" LX 200, 10" Dob, ST-80, ST-237, MX7C
        >>37 08 24 N 121 36 25 W
        >>http://www.employees.org/~ibarker/Astronomy
        >>
        >>
        >>To unsubscribe from this group, send an email to:
        >>ccd-newastro-unsubscribe@egroups.com
        >>
        >>
        >>
        >>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
        >>
        >>
        >>
        >>To unsubscribe from this group, send an email to:
        >>ccd-newastro-unsubscribe@egroups.com
        >>
        >>
        >>
        >>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
        >
        >--
        > Ivor Barker
        >AIM - rekrabrovi
        >10" LX 200, 10" Dob, ST-80, ST-237, MX7C
        >37 08 24 N 121 36 25 W
        >http://www.employees.org/~ibarker/Astronomy
        >
        >
        >To unsubscribe from this group, send an email to:
        >ccd-newastro-unsubscribe@egroups.com
        >
        >
        >
        >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
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