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'Onion ring' artefacts - a possible processing strategy?


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I was out imaging Jupiter again last night under pretty awful seeing conditions. The appearance of the dreaded 'onion' ring' artefacts reared their ugly head as I tried to extract a sharp image from the data using Wavelets. However I tried the waveklet configuration, the apperance of 'onion ring' artefacts put a limit on the amount fo sharpening I could apply.

From what I can surmise limb darkening on planetary images can cause ‘onion ring' differentiated concentric bands to appear as the radial gradient is sharpened.

So how to overcome this problem? I am no image processing whiz kid, but it struck me that if one could remove the limb darkening prior to sharpening, then reinstate the limb darkening again after sharpening wards, this might eliminate these limiting artefacts.

So here is my proposed approach:

The solution - principles

  • Remove the limb darkening (maybe by adding a de-saturated, inverted featureless blurred image to the original image, thus removing the limb darkening?)
  • Sharpen this new evenly-illuminated disc image
  • Re-introduce the limb darkening to sharpened image
  • Apply this sharpened image as a luminance layer to the original image.

Comments please - might this work or am I just stupid/mad/ill-educated in the dark arts of what is possible to do with Photoshop?

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Sounds better than my approach - Shrink the image scale until you can't see it and then delete the file so no one will ever be able to recover such a horrible attempt at capturing a planet :icon_confused:

But seriously I am going to try your technique on my latest capture and see if it helps

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