MureDenoise settings in PixInsight to suit my camera ... help please?

[SlimPaling]

I spent a bit of time yesterday trying out the “MureDenoise” script in Pixinsight but I am having difficulty in working out the correct settings to suit my camera which is a Moravian G2 8300 Mark II CCD mono.

The MureDenoise settings that I need to adjust or calculate are ..

1)  In the “MureDenoise Detector Area box” … the “GAIN” in units of e-/DN    and “GAUSSIAN NOISE” in units of DN

2) In the “Denoise Box” … the “Variance Scale”

I have been trawling the ‘net but I am having trouble finding out how to find/calculate these values for my own camera … does anybody have ideas about this?

Cheers Mike

[Adam1234]

Hi Mike, I was playing around with this script myself yesterday and was also trying to work out these settings. 

For the Gain and Gaussian noise - PI can calculate these values for you using the MureDenoise Detector Settings script IF you have 2 uncalibrated flat frames and 2 uncalibrated dark frames. I did not have these (i discarded them once I made my Masters) so I had to calculate/estimate the values manually, it took a while but I think I managed it in the end. According to the scripts documentation, it is more accurate to have the detector settings script calculate these values for you.

Here's how I calculated these manually:

Gain (e/DN) = there's a process under Image, I can't remember what it's called, but it will tell you the gain value. E.g For my ASI1600mm at 200 Gain the value was 0.498e/ADU, but because my camera is 12-bit I had to divide it by 16 to convert it to 16-bit to get 0.03e/DN which seemed in line  with what other people reported. I'm assuming your CCD 16-bit, in which case you shouldn't need to convert. 

Gaussian Noise = this one had me stumped for a while, but it turned out it can be calculated by dividing the read noise by the gain (e/DN).

 

The variance scale is just how much noise reduction it will appy, so I guess start at the default 1.0, and reduce if the NR is too much. 

 

FYI I discovered that if you perform an STF after applying Mure it goes all horrible. Way around this is to apply STF before Mure and create a process icon for that particular STF, so if you remove the STF you can then apply the original STF. Or just don't remove the STF.

Hope that helps!

Adam

[TerryMcK]

To get the Mure settings you need two uncalibrated flats and two darks (or bias) frames.

• Drag them to the relevant fields then click Estimate
• Write down the Gain and Gaussian Noise. Yes pen and paper!
• Click Dismiss as you are done with this bit now.
• Next execute MureDenoise

It works great and here are the settings I use:

Gain and Gaussian noise are the only parameters I change but enter yours into the two fields. Offset is not the offset from darkpoint and should be left at 0.

I never use flatfield but you can use a calibrated master flat if you want.

Select the calibrated mono image you want to denoise normally something like an Ha for instance. 

You can play around with variance by making it less than 1.

Keep cycle spin at 8 and that's it. You should only run the DemureDenoise on linear mono images BTW.

The settings may change for different filters but on my Ha, SII and OIII filters there is no difference with my mono camera.

Edited December 24, 2020 by TerryMcK

[SlimPaling]

Adam and Terry .... many thanks for the replies.

You have given some every useful information here 🙂

Merry Christmas!

Mike