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Green Stars During Processing

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#1 Rick49

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Posted 21 April 2021 - 11:40 AM

When I added luminance into an RGB image it produced green stars. In photoshop I can use HLVG to get rid of the green stars that appeared during processing. Does anyone know how to get rid of the green stars in GIMP? I have tried using levels and curves but no luck. A google search didn't produce a result.



#2 Tapio

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Posted 21 April 2021 - 11:57 AM

It shouldn't do that.

Maybe you should adjust color balance before you apply luminance.



#3 bobzeq25

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Posted 21 April 2021 - 01:14 PM

An astro specific processing program (Astro Pixel Processor, StarTools, PixInsight...) will solve the problem, and provide _many_ other benefits.


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#4 Astrolamb

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Posted 21 April 2021 - 04:34 PM

When I added luminance into an RGB image it produced green stars. In photoshop I can use HLVG to get rid of the green stars that appeared during processing. Does anyone know how to get rid of the green stars in GIMP? I have tried using levels and curves but no luck. A google search didn't produce a result.

 

Bobzeq25 is right, but if you are just trying to learn right now with gimp my best guess without seeing your data and workflow is that the image you are adding a luminance layer to is not actually color balanced.

The best way to alter the colors in gimp is to use the "colors" drop down and go down to components, then select "channel mixer". From there you can alter the colors far more than you can with any other tool and they are altered as a whole instead of as shadows, midtones, and lights like other tools would do. 

It is best to try and balance your colors with this tool before you stretch if you can, if not you should use it immediately after stretching before you subtract the background. 

 

Also just to make sure, you are using a desaturated image as a layer and the layer is set to "Lch Lightness" or "Luminance" correct? 


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#5 calypsob

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Posted 22 April 2021 - 11:09 AM

Bobzeq25 is right, but if you are just trying to learn right now with gimp my best guess without seeing your data and workflow is that the image you are adding a luminance layer to is not actually color balanced.

The best way to alter the colors in gimp is to use the "colors" drop down and go down to components, then select "channel mixer". From there you can alter the colors far more than you can with any other tool and they are altered as a whole instead of as shadows, midtones, and lights like other tools would do. 

It is best to try and balance your colors with this tool before you stretch if you can, if not you should use it immediately after stretching before you subtract the background. 

 

Also just to make sure, you are using a desaturated image as a layer and the layer is set to "Lch Lightness" or "Luminance" correct? 

Just to add to this, green stars indicate the highlights in your channel mixer need balancing. Bring them back towards magenta.

 

I dont like using SCNR or HLVG anymore because it de saturates oiii and other very faint structures which may just have a bad color balance.


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#6 Rick49

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Posted 22 April 2021 - 09:35 PM

Thank you everyone for their feedback.  I will follow the advise and see what happens. I have installed Affinity Photo and am just learning the basics. 




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