MURE Denoise with ASI1600MM

[jlodge]

In the past I haven't had much luck with MURE, but having heard so many good things I've decided to try again. I have a ZWO ASI1600MM-Pro (12 bit) and I am trying it out on my Ha image (Gain 139 Offset 21) of the Horsehead nebula, integrated and then cropped, nothing else.

I used flatSNRestimator on my G139 O21 Ha flats to get the figures for my Ha data.

It gives me Gain 0.061 e-/DN and temporal noise of 715.11 DN.

In MURE, if I leave the Gain as 0.061, but divide the temporal noise by 16 to get 44.69 and put these values into Mure I get what looks like a nice smooth result. If I divide the gain by 16 then I get a horrible granular result, likewise if I don't divide the temporal noise by 16.

So is that correct? Leaving the gain given by flatSNRestimator as it is but dividing the temporal noise by 16 to give you the gaussian noise? Are temporal noise and gaussian noise one and the same, the difference being between 12 bit and 16 bit here?

I just left the Offset at 0, despite using an offset of 21 during capture, I'm not sure whether this is correct or not?

Also is it best to leave variance scale and cycle spin-count the default?

I have attached three images, one before MURE, one with Variance set to 0.8 and one with Variance set to 1.0 *Added in the reply below*

 

[jlodge]

Please see the attached stretched images, I have cropped a lot also.

 

[mschuster]

A gain of 0.061 e-/DN indicates that frames were multiplied by 16. This is OK as long as it was done consistently to all frames.

A temporal noise of 715.11 DN is likely the noise in flat frames. MureDenoise needs noise in bias or darks, not flats. Assuming all frames were multiplied by 16, I expect noise in bias to be somewhere around 30 DN.

Please try my new script MureDenoiseDetectorSettings. It replaces the old measurement scripts, is easier to use, and avoids some confusion. I will update MureDenoise tooltips and documentation soon to reference this new script.

Also, if possible please post a link to two uncalibrated flat frames and either two bias frames or two dark frames.

Regarding offset, PI preprocessing normally removes offset when light frames are bias- or dark-subtracted. A 0 offset setting in MureDenoise is correct.

Leaving variance scale and cycle-spin as defaults is OK. You need to make sure combination count and interpolation method are set correctly. Also, the latest MureDenoise version has a new option use image metadata. You should check this box also.

 

[jlodge]

Thank you Mike, where do I download the MureDenoiseDetectorSettings script please? I've had a look in the resources here http://pixinsight.com.ar/en/docs/ also the new scripts forum and a google search with no luck.

Here is a Dropbox link for the flats and a master flat dark https://www.dropbox.com/sh/uzhn3rjoz9ysi6k/AACvxedocz-Y2jmII5XNmV8ua?dl=0 unfortunately I deleted my uncalibrated darks and flat darks and only have masters now, I can make some more though as I need to do some anyway for some recent data.

Yes I have used the image metadata option thank you, more convenient for sure!

On a separate note, did I understand the documentation correctly that if I use the Drizzle algorithm in my integration stack then MURE will not work properly? I have not done so here because dithering was not used during acquisition, however on newer targets I have dithered between frames.

 

[mschuster]

Thank you. The new MureDenoiseDetectorSettings script should appears as an auto update. Please try Resources > Updates > Check for Updates. It should appear as Script > Noise Reduction > MureDenoiseDetectorSettings.

You will need two raw uncalibrated flats and either two raw bias or two raw darks for MureDenoiseDetectorSettings. Masters and calibrated frames will not work.

MureDenoise does not work with drizzle.

 

[jlodge]

Using Resources > Updates > Check for Updates I don't get any new updates. In Script > Noise Reduction I only have MureDenoise.

Do I need to add an additional repository? I just have the default ones as in the attached screenshot.

 

[mschuster]

Those repositories are correct. I don't know why an auto update has not appeared.

I will post a link later today which you can apply manually.

 

[Juan Conejero]

Indeed those repositories are correct for version 1.8.8-2 of PixInsight. You should have received the MureDenoiseDetectorSettings script as a regular update. Otherwise something strange is happening with your PixInsight installation. A virus protection application messing with application files, maybe?

 

[mschuster]

Thank you Juan.

jlodge, those flats do appear to be scaled up by 16, as all pixel values are multiples of 16. Had they not been scaled up, measured gain would be 16 times larger, about 1 e-/DN (as expected for the camera).

If you cannot resolve your update problem (you need other 1.8.8-2 PI updates also), here is a link to the MureDenoiseDetectorSettings script. Here is how to install it manually:

https://www.dropbox.com/s/bwilmq9h1mvia85/MureDenoiseDetectorSettings.1.1.zip?dl=0

Unzip to a folder
Script > Feature Scripts...
Add
Select the folder
Open
OK
Done

 

[jlodge]

Thank you Juan and Mike, I only use the built in Windows Anti-virus, it appears that MureDenoiseDetectorSettings has downloaded (see image), but for some reason it is not showing up in my Scripts in PI, what could be the reason for this?

Mike, I have added two uncalibrated flat dark frames to the dropbox folder for those flats already in there.

*EDIT* I have managed to add it through feature scripts and pointing it at Pixinsight/src/scripts/mschuster. Should it not add itself automatically?

 

[mschuster]

Thank you jlodge.

The two flat darks also appear to be scaled up by 16. This is good, as if any frame scaling is done, all frames should to be scaled likewise to avoid PI pre-processing havoc.

Given your flat and flat dark frames, MureDenoiseDetectorSettings report gain 0.061 e-/DN and Gaussian noise 27.71 DN. Both are what I would expect for this camera with 16x frame scaling. These are the values to use in MureDenoise as long as your light frames were also scaled 16x, which I am guessing is very likely.

Regarding why the update was downloaded and but not installed, I do not know.

Edit:

*EDIT* I have managed to add it through feature scripts and pointing it at Pixinsight/src/scripts/mschuster. Should it not add itself automatically?

Yes, I think it should have been.

 

[jlodge]

Thank you Mike, yes I have just used MURE on my image and it produces a very pleasing result.

Thank you so much for taking the time (on a Sunday as well) to help me out.