Author Topic: Deringing support in Deconvolution  (Read 2887 times)

Offline astroedo

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Deringing support in Deconvolution
« on: 2013 May 04 05:43:51 »
Hi to all forum users.

I'm moving my first steps in deconvolution world with a few nice results.
But now I have problems in building a deringing support mask for a particular image.

I'm trying to deconvolve the linked M81 image (download from http://www.radice.biz/SHARE/M81_Luigi.zip it's a small crop of the original image obtained with a Canon 5D camera: background corrected, white balanced and denoised with ATWT ).

I've built a PSF image using DynamicPSF tool but I'm not able to build a suitable star mask for Local deringing support:
I continue to have strong ringing artifacts around bright stars superposed to M81.

Could someone give me some advice or, better, process icons in order to achieve the best parameters to use in Starmask tool and in devonvolution?

Thank you in advance

Edoardo

Offline Alejandro Tombolini

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Re: Deringing support in Deconvolution
« Reply #1 on: 2013 May 04 12:51:13 »
Hi Edoardo,

I wouldn't apply ATWT for denoise before deconvolution, or if do it, only very little amount as it has already generated some artefact in the background that will be considerally increased when deconvolve the image.



Generate a PSF to be used as external PSF in Deconvolution



Applying Deconvolution with the PSF and values by default tipically will show rings in stars and the cores of the bigest stars will get darker, It can be seen clearly when the image is not stretched



Then it is conveniente to use a mask to protect the cores of the big stars
The dark rings will be solve almost completely using Deringing and adjusting Global dark, however usually it is helpful add some proteccion with starmask for those big stars
Generate a starmask to protect stars:



Then apply Deconvolution protecting stars and adjust Global dark conveniently to avoid rings.



It also could be helpful to enhance portection in stars that maybe are not correctly protected with the starmask. Then I create another starmask with the structure detection mode activated, to be used as Local deringing and it help in some medium size stars that were not completely protected with the starmask.



The star at the right is better protected using Local support





Saludos, Alejandro.

Offline astroedo

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Re: Deringing support in Deconvolution
« Reply #2 on: 2013 May 05 05:48:32 »
Thank you Alejandro for crystal clear workflow.

My main error (besides applying noise reduction before deconvolution  :-\ ) was to not apply protection on bright stars thinking that a good  deringing local support could be enough.

indeed i applied a luminance mask to protect dark areas doing exactly the opposite of the right thing: apply a stronger deconvolution on brighter stars.

The only modification to your workflow I've done is to keep my luminance mask but multiplying it by the pixel inverted star_mask

M81_LumMask*~star_mask


is this correct in your opinion?


Thank you again!!!!!

Edoardo

Offline Alejandro Tombolini

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Re: Deringing support in Deconvolution
« Reply #3 on: 2013 May 05 15:10:48 »
Hi Edoardo,

If the idea is to protect stars and background at the same time, yes. And in that case you will probably need to change Deconvolution parameters, as the actual I think are not enough to see changes.
Any way, I usually prefer not to protect the background with masks and control it with Wavelet Regularization in Deconvolution tool and finding the best parameters of deringing.

waiting for the final result  :)

Saludos.
Alejandro.