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NGC 6823 & NGC 6820

by Alejandro Tombolini

Introduction

Image of Christoph Puetz publicated in Image Processing Challenges - Complete description of a very weak nebulae - Main notes: MaskedStretch, Saturation, ATWT for Chrominance noise reduction, LogStretch. Date: Aug 2012.

Processing

First I have used HistogramEqualization to see the information in the image and select a place where to make the preview for use in BackgroundNeutralization.

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After that CBR to remove the horizontal banding in the bottom of the image.

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Once again helped with HistogramEqualization detect the places where to place samples for use with DBE. (Generate a clone, make samples over it, generate the DBE instance and then apply on the image)

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ColorCalibration using the same preview used for BackgroundNeutralization as Background Reference image and the complete image for White reference image.

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Generate the PSF and use it in Deconvolution protecting stars cores with starmask.

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A sequence of Masked Stretch until Target median of 0.4. This is time consuming when you save the project and I must apologize at this point because I could not save the project every step, and I can not remember if some other clips were applied in between in addition to the last shadows.

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With HT clip shadows.

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CurvesTransformation to increase contrast, saturations and colors.

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More contrast and Chrominace Noise Reduction using ATWT.

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SCNR to eliminate greenish.

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Noise reduction with L mask protecting stars using GREYCstoration.

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Still looking for more contrast use LHE with the same L mask protecting stars (At this time I detect some problems in stars cores, maybe the previous L mask was not good enough and was caused for GREYCstration.

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Now I will built a mask without stars to protect bright nebulae and apply curves. As R channel has the information, extract it and duplicate, applying ATWT on duplicate to remove layer bigger than scale of 256 pixel,

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PixelMath to substract R_clone from R unchecking "rescalete" and after that apply ATWT to smoothness and built the rangemask over it.

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Protecting bright nebulae apply CurvesTransformation to desaturate background.

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Now invert the mask and apply CurvesTransformation to saturate nebula protecting background.

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ACDNR to reduce noise.

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With the R channel protecting background apply LogStrech to increase nebulae.

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As the halos in stars has increase considerable i will tray to reduce and adjust colors in the stars. For that build a mask to protect background and stars cores but not halos. The mask is the result of BlendScript multiplying the starmask and rangmask. See Blending Modes

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Apply CurvesTransformation in stars halos protecting with BlendMask.

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Final Unsharp without mask.

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Final Image:

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Last Update: 08/07/2014 02:55 UT

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