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This Page shows my process for selectively applying the PixInsight HDR Multiscale Transform (HDRMultiscaleTrans).

Normally, this should be applied to 32 or 64-bit floating point data. With these images, the bright galaxy core data is usually useable, even when it appears completely burned out. In this case, we are using the final color image. The below image was saved as a 16-bit TIF, from Photoshop, for loading into PixInsight.


The below example is a screenshot of the HDRMultiscaleTrans dialogbox with settings that I typically use. For smaller galaxies, using only four layers often works better. Simply try different numbers to get the desired effect.

If the image has galaxies sizes that greatly differ, it may be necessary to do two separate transforms. I may use five layers for the larger galaxy and four for the smaller ones. In this case, blending these two images, with the original data, becomes a two-step process..

Also experiment with the number of iterations. However, I found that only one iteration usually works best.

There are a few other settings. So by all means experiment with them all.


The below image shows the result from applying the settings in the above dialog box.

The next image shows the result blended with the original image at 65%.

The final image is simply the original shown for comparison.

If you like the result of the transformation, then you are finished. However, in this case, I find the affect a bit too aggressive. Also, I don't like what the transformation did to the stars. So I have chosen to only blend the galaxy data with the original image.

This is a simple PhotoShop process. First, paste the transformed image onto the original as a new layer. Then adjust the opacity for the second layer... 65% was used for this image. Use the lasso tool, with appropriate feather settings, to select the two galaxies. Forty was used for the large galaxy and 10 for the smaller. Finally, invert the selection, cut away everything except the galaxies and flatten the image.