Fourier transform - what to clone stamp

[cwiede]

Hi,
I have a solar H-alpha image, which shows a stripe-pattern in parts of the left half of the image. I don't know where it comes from, but I wanted to erase it with the Fourier transform tool. However I find it difficult to understand what to erase in the fourier transformed images (using clone stamp). Can anybody help me to understand the fourier transformed images better? As far as I know high frequency structures should correspond to pixels in the center, right? So the stripe-pattern should be somewhere far from the center. I attach the image and the fourier transformed images as jpg. You can download the original fit file here (7MB):
https://www.wuala.com/cwiede/public
Best regards
Christof Wiedemair

[oldwexi]

Hi Christof!
Cannot recommend to use Clonestamp.
One Solution of many is to extract the stripes with MultiscaleMedianTransform Wavelet Layers.
Cooking recipe:
Rename Original Image to   "o"
drag over "o"  MultiscaleMedianTransform    8 Layers, Layer 6  -0.200,     Layer 7 -1.000,   Layer 8  -0.200
clone result, rename to "f"
PixelMath:   o-f     create new Image Name "diff"

This results in the wanted structure.
Stretch "diff" with STF -> Histo.
Use "diff" as Mask over "o" and
reduce with Curves the bright stripes in "o".

Gerald
Resulted Image at:
http://www.werbeagentur.org/oldwexi/gallery_deepsky/pixinsight_MMT.jpg

[Carlos Milovic]

I wouln'd recommend CS + Fourier either. These stripes have a medium frequency, so it is located close to the center of the fourier space. There, isolation of structures is more difficut, so is highly likelly that you'll end generating artifacts.
I liked a lot Gerald's multiscale suggestion.

[cwiede]

Hi Gerald,
works perfectly! Thank you very much! The mask protects more than just the stripes, but the result looks very good. I have to read more about this MultiscaleMedianTransform-Tool!
Best regards
Christof