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Assembly ha and O3 for black and white luminance

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#1 miela74

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Posted 22 August 2019 - 08:02 PM

Hello everyone,

 

I want to assemble a series of images in HALPHA and O3 to make a beautiful luminance in black and white but I do not know how to do under pixinsight and what are the parameters. I have a lot of images 160 for the O3 and 150 for the HA

 

Thank you for your answers.



#2 Ken Sturrock

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Posted 22 August 2019 - 08:44 PM

Moved to a beautiful forum about imaging.


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#3 Becomart

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Posted 23 August 2019 - 02:14 AM

If you combine two channels, you’re going to get a colour image. You can, of course, return it to a black and white image through colour balancing, desaturation, etc. What software are you using? You can also combine the channels and extract the luminance in software like Pixinsight. 


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#4 miela74

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Posted 23 August 2019 - 09:33 AM

Hello,

 

I use pixinsight and I would like to know what is the best way to get a nice luminance combined with these two filters, even under photoshop, either pixinsight or photoshop. Of course, I can not stack 300 images. So I did a stacking for the HA and a stacking for the O3

Thank you for your answer and excuse the bad place in the forum, I get lost a little.

 

Good black sky



#5 pfile

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Posted 23 August 2019 - 10:45 AM

add the Ha master twice, and the O3 master twice to ImageIntegration (so that there are 4 files) and then just run ImageIntegration with default settings. you'll get a noise-weighted mono image which is the combined L for those two input images. you need to add them twice only because ImageIntegration needs 3 or more images to integrate.

 

rob



#6 WadeH237

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Posted 23 August 2019 - 11:30 AM

In the simplest terms, you can just use PixelMath with an expression like this:

 

Ha / 2 + OIII / 2

 

That will give you a monochrome image with data from both filters.  The issue that you'll run into is that the relative contributions of the two bands are probably going to vary wildly, based on the target object.  In some cases, the Ha will dominate and the OIII will be almost invisible.  And in some cases, it will be reversed.  There are two ways that you can address this issue.  First (and simplest), you could just do a LinearFit on the dimmer of the two images, using the brighter of the two as the reference.  That will ensure that both images contribute more or less equally.

 

The issue is that you may not want equal contribution.  In that case, there are various ways to use PixelMath to adjust the contribution, ranging from really simple to pretty complicated.  The simplest way to just to play around with the "divided by 2" parts of the expression above.

 

Personally, I generally combine the channels into an RGB image with PixelMath.  I have a few expressions that equalize the background sky level and adjust the slope of the dimmer image to get the level of contribution that I want (I get the values for my expressions using previews of interesting areas of the uncombined images).  Once I have the color image balanced to taste, then I extract the luminance.  This results in a black and white image that has the specific contributions for each of the channels that I want.



#7 2ghouls

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Posted 23 August 2019 - 12:29 PM

Hello,

 

I use pixinsight and I would like to know what is the best way to get a nice luminance combined with these two filters, even under photoshop, either pixinsight or photoshop. Of course, I can not stack 300 images. So I did a stacking for the HA and a stacking for the O3

Thank you for your answer and excuse the bad place in the forum, I get lost a little.

 

Good black sky

A little bit confused. Is your end goal a black and white image? Or are you using the Ha+O3 combined luminance to enhance a color image?

 

Rob and Wade explained two ways to do it in PixInsight. In Photoshop, you can open the Ha, then File->Place... the O3 on top and set it's blend mode to "screen". The image may then appear a bit too washed out. You can just add a levels and/or curves adjustment layer to set the black point and contrast to where you like them.



#8 miela74

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Posted 24 August 2019 - 04:30 PM

Thank you for your answers, I hope it will work. Thank you




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