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Green Color in Orion

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#1 sandconp

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Posted 02 January 2021 - 12:58 AM

I noticed in my M42 image some green which I have never seen before after processing it with PixInsight.  I am not sure if I was using my Optolong L-Enhance filter or just the Pro Model with my Hyperstar when I took the image.  I compared it to some of my older Orion images and I don't see any green in those images.  I realize that I can take out the green using SCNR in PixInsight I don't know if I should bother.

 

 

 

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Edited by sandconp, 02 January 2021 - 01:13 AM.

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#2 bobzeq25

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Posted 02 January 2021 - 01:28 AM

I use SCNR to reduce excess green on most images.  And certainly with one shot color, where the bayer matrix tends to emphasize green.  50% green pixels, and sloppy spectral curves that register some blue and red as green.  That sells terrestrial cameras, people tend to like strong greens.

 

That's a big reason SCNR exists, and it's certainly why the default is green.  Why StarTools lets you change some green to yellow or brown.

 

Try it.  I think you'll like the result.  I do it right before color calibration so that step doesn't have to deal as much with excess green.


Edited by bobzeq25, 02 January 2021 - 01:34 AM.

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#3 sharkmelley

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Posted 02 January 2021 - 02:54 AM

I noticed in my M42 image some green which I have never seen before after processing it with PixInsight. 

I think you are using the wrong Bayer pattern when debayering. Your green areas are the H-alpha areas and they should appear red.

 

Mark


Edited by sharkmelley, 02 January 2021 - 05:18 AM.

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#4 sg6

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Posted 02 January 2021 - 04:25 AM

Interesting replies: My reason for this is that when people have looked at M42 in a large reflector eyeball only the one color they usually say they can make out is a green tinge.

 

Most images of M42 seem purple these days. Cannot recall anyone saying they saw visually purple.

 

So has artistic interpretation taken over from reality?

Have sufficent people removed green that it is now considered unacceptable?

As in Bob, Harry, and Jims images have no green, I had better remove the green in mine.

 

Have a search for M42 images and you literally get every color known to mankind, and I suspect a few that are unknown. So I would expect some green. How much? Not so sure about.

 

Could try and find a "realistic color image of M42" however I oddly have doubts you will be greatly successful.



#5 Apagador

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Posted 02 January 2021 - 04:43 AM

https://clarkvision....ium.true.color/

 

Interesting read smile.gif



#6 sandconp

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Posted 02 January 2021 - 02:10 PM

I think you are using the wrong Bayer pattern when debayering. Your green areas are the H-alpha areas and they should appear red.

 

Mark

I did not know that I had a choice of which de-bayering pattern I can use?  I was using PixInsight using the WBBP script with the CFA Option checked.



#7 Cfreerksen

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Posted 02 January 2021 - 02:17 PM

I did not know that I had a choice of which de-bayering pattern I can use?  I was using PixInsight using the WBBP script with the CFA Option checked.

If it is the wrong debayer pattern causing the issue you can set it here. Automatic is probably set right now. I had issues with some camera and set mine to RGGB which is correct for my cameras.

 

Chris

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Edited by Cfreerksen, 02 January 2021 - 03:46 PM.

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#8 jonnybravo0311

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Posted 02 January 2021 - 02:20 PM

I did not know that I had a choice of which de-bayering pattern I can use?  I was using PixInsight using the WBBP script with the CFA Option checked.

Here:

 

Pi wbpp debayer choices


#9 bobzeq25

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Posted 02 January 2021 - 03:43 PM

Interesting replies: My reason for this is that when people have looked at M42 in a large reflector eyeball only the one color they usually say they can make out is a green tinge.

 

Most images of M42 seem purple these days. Cannot recall anyone saying they saw visually purple.

 

So has artistic interpretation taken over from reality?

Have sufficent people removed green that it is now considered unacceptable?

As in Bob, Harry, and Jims images have no green, I had better remove the green in mine.

 

Have a search for M42 images and you literally get every color known to mankind, and I suspect a few that are unknown. So I would expect some green. How much? Not so sure about.

 

Could try and find a "realistic color image of M42" however I oddly have doubts you will be greatly successful.

I have no doubt that you won't be successful in finding a "realistic" color image of anything.  <smile>

 

The topic is well covered in the superb books "Lessons from the Masters" and "Coloring the Universe".

 

https://www.amazon.c...l/dp/1461478332

 

https://www.amazon.c.../dp/1602232733/



#10 bobzeq25

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Posted 02 January 2021 - 03:48 PM

I did not know that I had a choice of which de-bayering pattern I can use?  I was using PixInsight using the WBBP script with the CFA Option checked.

PI's auto color array selection often does not work.  You need to know what your camera's is, and where to specify it, although RGGB will most often work.

 

Another reason I don't recommend PI to the average beginner.  And I definitely recommend they use the individual calibrating/stacking tools, not the scripts.


Edited by bobzeq25, 02 January 2021 - 03:48 PM.


#11 descott12

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Posted 02 January 2021 - 03:48 PM

That is definitely an unusual color scheme but I really like it. Very subdued and subtle. From a purely artistic standpoint, I wouldn't change anything.



#12 sharkmelley

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Posted 02 January 2021 - 05:47 PM

My reason for this is that when people have looked at M42 in a large reflector eyeball only the one color they usually say they can make out is a green tinge.

Yes, that is more or less the true colour:

https://clarkvision....ium.true.color/

 

Mark



#13 sandconp

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Posted 02 January 2021 - 06:04 PM

If it is the wrong debayer pattern causing the issue you can set it here. Automatic is probably set right now. I had issues with some camera and set mine to RGGB which is correct for my cameras.

 

Chris

That’s exactly what the problem was. For some reason I chose ‘GRBG’ versus ‘RGGB’ but my ZWO camera uses the bayer pattern of ‘RGGB’.

 

Thanks to all who responded.

 

I generally don't worry about this because I had been using Sharpcap but I have been using APT lately which requires the FIT image to be debayered.


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#14 Bill G.

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Posted 02 January 2021 - 08:55 PM

Yes, that is more or less the true colour:

https://clarkvision....ium.true.color/

 

Mark

Well, I guess that all depends on how you define true color.....

The human eye being most sensitive to green because it is roughly the center of the visible light spectrum. You see mostly green when the light is dim. Further dimming and you drop back to grayscale and no color at all.

But, increase the light level and other colors become more visible.

 

So, an argument can be made that the camera is seeing the true color and by eye we see mostly green because the light level is not sufficient even though the other colors are there. The bayer matrix has 2 greens to try and replicate the eyes sensitivity to green.... except that the camera does not lose the sensitivity to red and blue as the light level goes down like the eye does.

 

Just a thought..... smile.gif

 

Bill G.


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#15 sharkmelley

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Posted 03 January 2021 - 01:37 AM

Well, I guess that all depends on how you define true color.....

I define it quite simply.  It's the colour the eye would see if the intensity were increased to the point where the eye easily sees the colour.

 

Mark



#16 sbharrat

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Posted 03 January 2021 - 09:29 AM

I define it quite simply.  It's the colour the eye would see if the intensity were increased to the point where the eye easily sees the colour.

 

Mark

And from what we know of the actual makeup of Orion, this would be the pinkish/red scheme I am accustomed to seeing???



#17 Bill G.

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Posted 03 January 2021 - 09:31 AM

I define it quite simply.  It's the colour the eye would see if the intensity were increased to the point where the eye easily sees the colour.

 

Mark

I can agree with that...but isn't that pretty much what the camera (typical OSC) sees?

 

Bill G.

 

Btw, I like to get other people's perspectives. I learn  a lot that way. Please don't  take this as being argumentative.



#18 sharkmelley

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Posted 03 January 2021 - 10:24 AM

I can agree with that...but isn't that pretty much what the camera (typical OSC) sees?

 

Bill G.

 

Btw, I like to get other people's perspectives. I learn  a lot that way. Please don't  take this as being argumentative.

For the nebulosity around the Trapezium a OSC camera should produce a result near enough to the true teal colour.  However Hydrogen emissions such as those around the Horsehead will be rendered far more red than the true pink colour because a OSC camera has enhanced sensitivity in the red end of the spectrum, compared with the human eye.

 

Mark



#19 Bill G.

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Posted 03 January 2021 - 11:25 AM


Mark,
Again, in a lower light setting I would agree. But in a light intensity where the eye is working undiminished, most all OSCs (dslr/ml not AP) pretty well match what I see. Not a perceivable difference. In fact if my ML did not match what i see, i would not like it. I recall my first digital camera 640x480 (woohoo!) that recorded images on a 💾 floppy disk. Reds tended to be exaggerated and i was not happy with that at all...not to mention the resolution...but hey, it was new!

Now if we are talking AP OSC, then yes, I totally agree.

Bill G.

#20 sandconp

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Posted 03 January 2021 - 10:16 PM

My Corrected Image.

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#21 jonnybravo0311

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Posted 03 January 2021 - 10:55 PM

Those colors are much more typical :). If you haven't, grab the EZ scripts for PI and run the EZ HDR on your image. Might be able to get some detail from the Trapezium. Might not if it's completely clipped, but worth the try.



#22 sandconp

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Posted 04 January 2021 - 11:23 PM

Those colors are much more typical smile.gif. If you haven't, grab the EZ scripts for PI and run the EZ HDR on your image. Might be able to get some detail from the Trapezium. Might not if it's completely clipped, but worth the try.

Thanks I did not know about these scripts.




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