Mure Denoise and Drizzle Integration

[rdryfoos]

It is common knowledge that Mure Denoise is not supposed to be used on a drizzle integrated stack. However, I ran an experiment to see why this was so.  I drizzle integrated a stack of Ha subs (20 30 minute subs).  I then ran Mure Denoise with a noise estimate about 2/3 what I used in the non drizzle stack of the same subs, and a strength factor of 1/2 what I usually use, which is 1.0--so a setting of 0.5.

It worked--not as well as on the non drizzle integrated stack--but it improved the image--very similar in extent as removing the first wavelet layer with Multiscale Median Transfer.

So--my question--what is the technical reason why MD should not be used with drizzle integration?  Does drizzle completely change the image so MD removes signal instead of noise?  If so (but I think not), its obvious it can't be used.  But that is not what happened in my image.  But there might be detriments to the image that are not visible, or will not manifest themselves until much later in the processing work flow. 

Thanks--Rodd

[mschuster]

Drizzle introduces pixel correlations not modeled by the script. The ability to distinguish signal and noise is compromised. Signal may be lost. Artifacts are possible.

But if it looks ok and processes ok, then ok!

Thanks,
Mike

[rdryfoos]

Drizzle introduces pixel correlations not modeled by the script. The ability to distinguish signal and noise is compromised. Signal may be lost. Artifacts are possible.

But if it looks ok and processes ok, then ok!

Thanks,
Mike

  Well--it looks ok--you can't see the effects really until you zoom in to 10:1 or so, so its hard to tell if signal is being compromised.  That's true in general I find with Mure Denoise--its hard to tell when you have gone to far even with a non drizzled image.  I assume that the line you don't want to cross is WAY BEFORE the appearance of the stippled pattern that appears at 20:1 zoom.

[mschuster]

The up side is that it is OK to use the script anyway you want to.

The down side is that when you tweak the parameters to specify more noise than exists, or run unsupported images, you will likely loose signal and create artifacts.

Thanks,
Mike