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NGC 2359 - Thor's Helmet

by Alejandro Tombolini

Introduction

Image of Jules publicated in Image Processing Challenges - Complete description of a narrowband image - Main notes: Carefull DynamicBackgroundExtraxtion and CanonBandingReduction to rescue fines details in SII wich was quite weak. Date: Feb 2013.

Processing

First a Crop of the three channels:

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As I am using PixInsight 1.8 RC3 and do not have HistogramEqualization yet, I have used AdaptativeStretch applied to a clone of each channel to see and define background samples for DynamicBackgroundExtraction, generate the instance of DynamicBackgroundExtraction and then apply to the original channel. Same operation for SII and Hα.

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It was not necesary DBE for OIII, but CanonBandingReduction to eliminate the horizontal line that can be seen in the base of the image. The values of the script as follow.

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LRGBCombination R:SII, G:Ha, B:OIII.

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Select a small preview and BackgroundNeutralization.

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ColorCalibration. Same preview to be used as Reference image for Background Reference and the full image as Reference image for White reference. Note that I have unchecked the Structure Detection option.

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DynamicPSF to generate a PSF to be used in Deconvolution and Starmask to protect the core of the bright stars. Then apply Deconvolution with the following parameters:

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Consecutively twice MaskedStretchScript.
First 200 iterations, 0.1 Target median and Shadows clipping in the mask 0,01.
Second 200 iterations, 0.2 Target median and Shadows clipping in the mask 0,02.

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Autozero Shadows in HistogramTransformation.

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ATrousWaveletTransform for noise reduction using k-Sigma. (Juan, big, big improvement to have RTP for k-sigma noise thresholding, now this tool has no limits)

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Clone SII, and apply HistogramTransformation and ATrousWaveletTransform to smooth and generate a mask to be used with CurvesTransformation.

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Increase color and Saturation protecting bright areas.

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Chrominance noise reduction with ACDNR without mask.

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HDRMultiscaleTransform to increase details in bright areas, protecting stars with starmask.

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Using the same Starmask to protect stars, apply LocalHistogramEqualization. Note that STF is active to visualize the process applied. The image in the left shows the actual stretch.

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ATrousWaveletTransform to reduce noise and high light areas protecting bright parts of the nebulae with RangeMask.

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Generate a new RangeMask over a clone of SII previously stretched with AdaptativeStretch and apply CurvesTransformation protecting bright areas.

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Noise reduction to Chominance and Luminance protecting the nebulae with RangeMask.

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HDRMultiscaleTransform twice, first 4 layers and finally 2 layers.

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Transfer the STF to HT and apply.

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To reduce stars, first generate a StarMask and apply MorphologicalSelection protecting background.

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Second, with the same starmask, adjust curves and green on stars.

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New starmask to protect stars and increase details in the nebulae with UnsharpMask.

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Last noise reduction using MultiscaleMedianTransform tool in layers 1 and 2.

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Final Image:

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Last Update: 29/03/2014 04:08 UT

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