How do I create the effect that is shown in Adobe Lightroom Sharpening - Masking - preview?

Question

Yesterday, I photographed the comet C/2020 F3 ("NEOWISE"). I took several images and stacked the best ones using Deep Sky Stacker. I post-processed the image using Adobe Lightroom.
Normally, when I sharpen my images, I use the preview function when moving the slider with my mouse, by pressing the Alt (or Option on Mac) key. This shows a processed, grayscale image, that helps to get the "right" amount of the effect I'm working on, without overdoing it (See Adobe's help page on this topic).
I was sharpening my NEOWISE image, and when adjusting the Masking slider of the Sharpening option in Adobe Lightroom CC, pressing Alt/Option showed an amazing detail in the tail of the comet (see picture of my monitor below).
My questions are:

What is the effect/process that Lightroom shows when Alt/Optioning the Masking slider?
Can I recreate this effect in Lightroom or Photoshop, and how?

Processed image of NEOWISE:

Photo of my monitor with the desired effect:

hpchavaz · Answer

Masking is masking, it limits where the sharpening will occur.
Your question is therefore not as simple as it looks as there are at least three steps:

the algorithm producing the mask
the sharpening algorithm
the algorithm using the mask to limit the sharpened area

The artifacts in the image could be the result of the interaction between these three stages.
It is also possible that that these three steps are combined into one, but the resulting algorithm must be complex to say the least.
Personally, I would first try to work with Photoshop in the following way:

layer duplication
application on the top layer of a sharpening filter
on this top layer masking out of the comet with full opacity (black)

Then, as long as the result is not satisfactory or for the fun of it, you would search for a sharpen algorithm for the comet on its layer, as far as one exists because trying to enhance sharpness in blurred areas is rarely a good idea.
This process would limit complexity by avoiding the above-mentioned interaction of different algorithms.

How do I create the effect that is shown in Adobe Lightroom Sharpening - Masking - preview?

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