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Dual Band Narrowband Filter Test

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#1 wb6pco

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Posted 23 June 2022 - 03:41 PM

This wasn't as time consuming as I thought it might be.

 

Reference this image:

 

 https://dl.dropbox.c...B_Test.jpg?dl=0

 

This image was taken with the Optolong L-eXtreme H-a / OIII filter.

 

The first image illustrates what happens when you have only H-a and 0% OIII. Hue is fixed, Saturation is fixed and Brightness varies from 0-100%. The only details you can see are the brightness differences your eye can differentiate in pure red. The human eye is not particularly good at this.

 

The second image illustrates a normal H-a / OIII image when the image data is equal in the green and blue channels. A photo of the moon will produce a normal grayscale image. Hue is fixed, Saturation is 0-100% and Brightness is 0-100%. In this image varying two of the three HSB parameters produces an image in which we can see more subtle detail.

 

The third image illustrates a small non-linear stretch to the blue channel which introduces a small shift in hue. Instead of pure red, the hue now varies from 330° (magenta) to 360° (0°) (red). I'm betting most people will find this image a bit more appealing than the red only hue of the second image.

 

Chuck

 


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#2 SgrB2

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Posted 23 June 2022 - 04:20 PM

I get that you're using a dual band filter for the observations.

What software are you using to set all the OIII to red in the first one?

What would the image look like if you didn't do any fiddling?  I'm confused....



#3 wb6pco

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Posted 23 June 2022 - 05:19 PM

I get that you're using a dual band filter for the observations.

What software are you using to set all the OIII to red in the first one?

What would the image look like if you didn't do any fiddling?  I'm confused....

I used Photoshop to eliminate the green and blue data. The second image is the normally processed image using proper white balance. Attached are the Curves used on the image to show just the red data.

 

Chuck

Attached Thumbnails

  • Photoshop_Curves_Red_Image.jpg

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