Why do i lose so much detail/data of Ha ??????

[Nikolas74]

Hi , 

i always have the same problem when i try to create an RGB image from narrowband images.....

The Ha detail/data gets so faint on the RGB end result....if i strech it gets worse....

How can i enhance the RGB image with all the Ha data.......????????

On the left is the Ha and on the right is the RGB from Ha + Oiii......

Nikolas.

 

[carastro]

I tend to add the Ha a second time as a luminance layer.  this does require some colour adjustment.

This is what i did with your image.  Bit rough and ready - I didn't do it too carefully as it is just an example, and I seem to have exaggerated the magenta corner top right, and was working with the screen shot, but just to give you some idea.  I use Photoshop not Pixinsight but I am sure there is a method in PI.

 

 

 

Edited November 18, 2019 by carastro

[vlaiv]

What sort of composition of Ha and OIII did you use?

I can see two issues with right image that don't "appear" on left one.

First is related to how human eye sees color, it is matter of perception. Not all colors when saturated to maximum have same "brightness" (we don't see them as equally bright). Here is image that can show you that:

If you don't pay attention to numbers - and just look at two sets of circles you will notice that left set of circles looks equally bright as right one (only missing the color - left one looks like right image in monochrome). Numbers are percent of full brightness. So red color carries about half the brightness of same intensity white.

When you stretch your data in mono / black&white (Ha data for example) and then apply red color to it - it will loose some of the perceived brightness because you are in fact just coloring it.

That is the reason why left image looks more pronounced than the right, although respective intensities of white and red are equal.

Another thing that does not look right with right image is color gradients. When you have mono image that is full of nebulosity - it is hard to tell that there is gradient. Our brain just interprets that as part of nebulosity.

Once you add color in that - gradients become obvious as "out of place color" - that is another thing that is happening to the right image.

You need to remove those gradients to get better looking image.

[Nikolas74]

4 hours ago, carastro said:

I tend to add the Ha a second time as a luminance layer.  this does require some colour adjustment.

This is what i did with your image.  Bit rough and ready - I didn't do it too carefully as it is just an example, and I seem to have exaggerated the magenta corner top right, and was working with the screen shot, but just to give you some idea.  I use Photoshop not Pixinsight but I am sure there is a method in PI.

 

 

 

Thank you !!!! that's a lot of improvement !!!!!!!

[steppenwolf]

Here is my down and dirty attempt on your screen dump.

1. I blended the Ha into the red at 40% and then replaced the red channel in your RGB Image.

2. I then blended the Ha again into a copy of the new 'Red' channel at 60% to form a new composite Luminance channel

3. I removed some of the background gradient in the RGB image

4. I added the Luminance channel to form an LRGB image.

I used PhotoShop for this process combining method but a similar result could be produced using PI and PixelMath

[Nikolas74]

WOW !!!!!!!! Thank you Steve......

All the info given from all of you are very helpful ......

Thank you all !!!!!!!!!!!!!!

Nikolas.