Noise Reduction in ATrous Wavelet

[dhalliday]

Hi everyone

Rumor of my death have been greatly exaggerated...but I have not been paying attention to this forum...as I should be.
My loss...
So after 10 minutes here I see a question (and answer) about settings in ATrous...I am assuming on linear data...
And low and behold I try these settings...and seem to get a fabulous result...!
So now I am feeling real bad...some ? 3 years in here...
I have been mostly using ACDNR...(on stretched data)...
Because it is NB mono data this has worked...(some)
But now its time to try a little harder...(part of which is spending more time around here...
(sorry folks)
Could someone start at step 1 and discuss this linear NR for me...?
Or share a good link/tutorial...?
On the plus side at least I have set up a group for Pixinsight users on Flickr..but it is an image posting site only...
http://www.flickr.com/groups/pixinsight/

So again...hope someone can sort me out.
Here is the (new) result;
http://www.flickr.com/photos/daveh56/6797906421/in/photostream
and here is the ACDNR result;
http://www.flickr.com/photos/daveh56/6786585629/in/photostream

It certainly seems this is whole aspect of NR that I have failed to come to grips with...

Dave Halliday

[Harry page]

Hi

Might give you a start http://www.harrysastroshed.com/at%20noise.html


Harry

[dhalliday]

Harry
Well...I should have just known you would have a video...!
For whatever reason...the audio is super low...so your melodious cadence is lost in my cooling fan hum.
Obviously it looks like just what I need...so  I will have a go on my faster connection at work tomorrow.
Having said that...watching the silent video sort of reminded me why I have been slow to use this...
It looks darn "hokus pokus"....
But for sure I will focus more...
Why do we not tick off the "noise reduction" button at the same time...are we not doing some form of NR...?
(there are actually two of them...one in "Large scale tranfer function"...
What the difference..and what is "LSTF" anyways...?
Aywaus thanks..hope you are keeping well.
I mostly hang out on Flickr...you should join...we need you !

Dave

[dhalliday]

Harry
Just wanted to repost breifly saying that I applied this process to some old data with good results...
http://www.flickr.com/photos/daveh56/6798326123/in/photostream/lightbox/

I will certainly have pen (and cap) in hand when I watch the video.
Thanks !

Dave

[dhalliday]

OK...Just saw the video...(and was playing more the process more last night..)
Pretty impressive...shows me what a damned fool I have been for not figuring it out sooner...

I also was confused about the (stretched) mask previously.
I need to hang out here a lot more...!

But I have sworn off emoticons...so hopefully I will be OK..


Dave

[Harry page]

Hi

Glad you worked it out    Makes a very good job of things does this noise reduction using AT 

Harry

[dhalliday]

Yes..lovely....My sky has gone from sand (or gravel) to talcum powder......
What about the kSigma do dad...?
When is it used ?
Deringing..?
Bias..?
etc

I see there was a prior discussion (started by you !) on this which resulted in the video...so I feel a bit better.
Obviously I need to parse the existing contents of the forum more..
Hope the shed is treating you well

Dave

[Harry page]

Hi

Well the K sigma ---------- I ain't got a scooby 

The deringing is used to reduce artifacts around things like stars when say using the Bias to sharpen your image

But this is another 38 tut vids 

Harry

[dhalliday]

It seems not so simple at second glance...
I have tried a few other images and sometimes see "oversmoothing" of the image...often with a rather "milky" sky as well...
We see that a bit here..
http://www.flickr.com/photos/daveh56/6797906421/in/photostream

Also I sometimes have individual surviving hot pxels...stretched they are easy to ACDNR away...but with ATrous they seem to get a bitt bigger...look worse..

Do we have a link that discusses the fine tuning of the settings..?
Maybe the depth of the mask is the issue..?
If I clip the mask a bit maybe the sky can be further  "nuked" by this NR..?
Or bad idea ?
Also...my mask has sky noise in it a lot sometimes..apply GreyC first or ?
Any further thought appreciated..

[Harry page]

Hi

I have never found a need to play with the Lum mask , but there might be a first time 

If you find the effect to much try reducing the threshold on the larger scales or even do not apply it at all at the largest scale

As with most noise reduction , less is better 

Harry

[dhalliday]

Thanks Harry....
I knew that slider did something.....

Dave