Fixing Star color

[strivedi]

Zocky,

First of all, thank you very much for spending the time to do this.

I see that you do not have the orange colors that I get.

Can you give me your settings for LRGB combine and color calibration? I could not get such clean color.

I did do dark calibration, but the flats for each filter were from a much older run so you do see a lot of noise and vignetting, however the color issue does not appear in your processed image.

I look forward to your suggestions/settings.

Geoff - thanks for the pointer - I will check it out.


Shailesh

 

[Zocky]

Shailesh, I`ve noticed that you have halos around the stars on your RGB stack, so I did my ChannelCombination with supplied RGB frames.
As you can see, there are no halos on my RGB image, so try to find out what went wrong with your ChannelCombination.
Here is the processing work flow.

So, first on list is ChannelCombination.

[Zocky]

Apply DBE. Since your image is quite dusty try different settings.

[Zocky]

Next step is HistogramTransformation

[Zocky]

From stretched image extract L component.
   

[Zocky]

On L image apply DBE.

[Zocky]

Since this image is intended to give details in final image, you have to reduce noise. I`ve used ACDNR.

[Zocky]

Switch to RGB image, and apply SCNR to reduce green glow.

[Zocky]

Now tweak color calibration, and enhance saturation using CurvesTransformation.
Apply saturation for stronger effect, don`t worry if image looks strange. This image will only give color in the next step.

[Zocky]

Now you have to combine L with RGB. Use LRGBCombination, and don`t forget to tick the Chrominance Noise Reduction.

[Zocky]

Again apply CurvesTransformation to increase contrast on the image.

[Zocky]

Once more apply DBE. It will improve overall flatness and color calibration.
 

[Zocky]

And here is the final result.

[strivedi]

Zocky,

I thank you again for your help and detailed post, you are awesome.

Now I know what I did wrong:

a) I went straight to LRGB combine (with L disabled) instead of Channel Combination. If do LRGB combine then I consistently get orange stars and halos. Interestingly that is the only flow I learned from Harry's newbie tutorials and it does not quite get colors correctly like Channel Combination

b) How did you figure out that my filters are dusty? I mean what did you observe in the images?

c) The simplest way I learned to apply HT is through the screen stretch function, but I did not get such a clean Gaussian curve after HT via screen stretch. Can you please explain how you got such a clean HT curve?
 
Shailesh

[Zocky]

b) How did you figure out that my filters are dusty? I mean what did you observe in the images?

Go to Process/ImageInspection/Blink
In pop up window click folder icon and select your RGB files. Enter delay time ( 0.2 to 0.5) and pres play. Observe how there are spots that moves. This spots are dust particles. Now notice, that you have spots that are on each image on the same place, and the once that are moving. Spots which are moving are on filters, and spots which are static, are on sensor or CCD chamber window.