How to avoid and fix mottled background

[whitenerj]

Some of my images seem to always form mottled backgrounds as I process them. Once the mottling is there, how can it be fixed? Also is there anyway to avoid it using certain methods?

Jason

[sreilly]

Well you really need to give some information. What processes are you using that result in this background? What is your workflow?

[whitenerj]

Well I do the basic linear processing of STF, DBE, BN, CC, and ATT. Then in non-linear I use HT, CT for Saturation and contrast. Histogram equalization, TVGDenoise, unsharp mask, morph for star reduction.

The background gets mottled in all my images. Could it be my scope or is processing to blame. I am using an 80mm EON and SBIG STF-8300c.

Here is an example:

http://www.astrobin.com/129469/

Thanks, Jason

[sreilly]

While the example shows some aggressive processing what you need to do is pay close attention to when this "molting" takes place. And understand that STF isn't a process but just a screen stretch.  suspect that the molting is taking place in one of several areas if not more. Have you tried not using TVGDenoise or at least some other parameters? If I had to guess I would suspect ATT, unsharp mask, and TVGD as likely suspects. You may want to look at some reference videos or help files to guide you on these processes. Harry's do a very good job explaining the proper use.  http://harrysastroshed.com/pixinsight/pixinsight%20video%20html/Pixinsighthome.html

[oldwexi]

Hi Jason!
For sure ist not the scope.
This mottled background is always created with much to much and to strong denoising!
Would do some very careful, masked denoising before really stretching the image.
Also on the streched image use masked denoise only in very small doses and very carefully!

Gerald

[whitenerj]

Thanks Gerald. I will reduce my denoising next time.

Jason

[jerryyyyy]

My bet is that it is the TGVDenoise...

[jkmorse]

+1 on Jerry's comment, especially if you are de-noising in the linear phase.  MLT does a much better job there IMHO and has the added bonus of a built in masking tool.

Best,

Jim