updated: 2021-05-23


Purpose

Neutralizes the sky background of a color deep-sky image.


The background neutralization task equalizes the average red, green and blue components of a color deep sky image to yield a neutral gray rendition of the sky background. Neutralization is carried out by applying per-channel linear transformations computed from a set of pixels sampled on a background reference image.

Activation

Process 🡺 All Processes 🡺 BackgroundNeutralization

Input

DBE or ABE treated pictured, file names like  “*_i_c_DBE.xisf”, "*_i_c_ABE" or "*_i_c_DBE_ABE" from sub folder "aligned"

Output

Corrected image, file name “*_i_c_DBE_BN.xisf” or similar into sub folder "aligned"

Previous Step

DBE or ABE background extraction

Next Step

Tutorial

https://www.youtube.com/watch?v=JtA4UoaAAas  (Part 6  DBE - starts around timestamp 2m56s)


Step

Description

 Action

1
Open the image form the last step (background extraction)




2
Create a preview without any stars

Select a region without any stars and press ALT+N

3
Open Background Neutralization

4
Select previously created view

Lower Limit:  Lower bound of the set of background pixels. Background reference pixels with values less than or equal to this value will be rejected for calculation of mean background levels. Note that since the minimum allowed value for this parameter is zero, black pixels are never taken into account.


Upper Limit:  Upper bound of the set of background pixels. Background reference pixels above this value will be rejected for calculation of mean background levels.


Working mode:  


  • Rescale as needed
    Similar to rescale, but the target image is only rescaled if there are out-of-range values after neutralization. This is the default working mode

    .
  • Target Background: sometimes work fine if there a too many stars everywhere on the image, try following settings on the right that lead to good results with this image


before                              after






or use these settings:

5

Start the Process

Pull the blue triangle at the lower left corner onto you main picture, that starts the process.

6

Check for Improvements

use the undo / redo icons in the menu to switch back and for

7

Save the image 

file name like *_i_c_DBE_ABE_BN.xisf

8

Keep the preview window

it will be reused in the next step.

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