Ha Processing

Dynamic PSF. Select approx. 50 not saturated stars, all over the image. Then select all the entries in the table, CTRL+A, and export the PSF.

Deconvolution result.

Duplicate

The ringing support starmask

Exported PSF

Add the deconvolution mask to the image. Red protects.

In the Deconvolution dialog select the generated PSF as External PSF. Select deringing and add the starmask as Local support. The Global Dark and Global bright is trial and error parameters. Use previews to save processing time and to better see changes. Set Iterations, start with low value, 15-20, tune the global values, when proper values found increase iteration and fine tune the global values.

DBE to remove gradients. Often done before Deconvolution. Quality of samples better than quantity. Select free background for samples, avoid bright stars. Not easy on this type of image where there are almost no free backgorund.

The result of the DBE is a new image "free" from gradients. Verify often more than one DBE operation is required.

MakskedStretched is selected as initial stretch. The dynamic range of this image is wide so I prefer to “overstretch” then lower the intensity by use of curves and histograms stretch instead of the opposite that often lead to burned out regions. First set a preview on a neutral background.

Use Curves in two steps to reduce intensity an an adjustment of the contrast.

A compression of the small scales by use of HDRMultiscaleTransform to bring out details in the brightest/outher parts of the nebula. Done twice.

Use LocalHistogramEqualization for a small contrast boost.

A 180 degree rotation to get, for me, the best orientation.

A very small contrast adjustment by use of curves.

A bit darker by use of HistogramTransformation

Sharpen by use of Deconvolution

 

The purpose with this step is to sharpen the nebula without destroying neither the stars nor the background. Can be done by several other tools like Unsharprmask or MultiScaleMedianTransform but here I selects deconvolution. Morten Balling a Danish master of image processing gave me the tips. His tip includes two masks, a luminance and a star mask.

 

First step is to create a starmask. The main purpose it to cover the largest stars. It is important to avoid small structures because those structures are the target for this process step.

 

Next steps is to create a luminanse image, then by use of PixelMatch subtract the star mask.

Add the mask and set parameters in the Parametric PSF. Adjust Std.Dev and ringing parameters. Trial and error, use previews to reduce processing time.

Stretching and handling of details

 

The stars in the image is not good so substitute them with stars from another processed image. The simplest way is to first create a starmask, then use PixelMath to "add" the one with the good stars. First use the DynamicAlignmnet to align the "other" image to the Ha image. Select the Ha image as first image then select alignment stars.

s.

The result of the Pixelmath operation. Dark protects, so her it is easy to see the parts that will be processed.

Set the Target Baground value and then and select the preview as Region of Interest

Excute the alignment process. A new image with registred added to the filename is created.

Add starmask to protect everything but the stars

NGC6888 - Ha Pixinsight Processing

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MainWindow with images, masks and processes.A proper way to save as a project. Can easily be opened and used to inspect and improve an image.

Open the image in linear mode. The image is the result of running the BatchPreProcess script where sub exposures are calibrated registered and integrated. The images are calibrated by bias and flats

The Screen Transfer Function is used to do an auto screen stretch to inspect the image. No changes is done to the image data.

Deconvolution

The Deconvolution of the image needs protection of the background and a starmask to avoid ringing. First create protection of the background by making a duplicate of the image and on the duplicate do a histogram stretch. Set the stretch level by use by used of the ScreenTransferFunction.

Set identifier on the mask to make it easier to find/identify.

ScreenTransfer to stretch deconvolution mask

A starmask is needed to support deconvulution process to avoid ringing. Important to set the Midtone value low since the mask is created on a linear image. The rest of the values are as many other Pixinsight parameters a matter of trial and error.

Pixelmath to add the stars

Final Image, press on image to inspect result