Although i have only been using PI for a couple of months, I think I have sharpening with MMT (basically same process for ATWT) down pretty good, at least for my needs. I use MMT instead of ATWT because of the ringing issue - I have used MMT for layers 1 and 2 and ATWT for 3 and 4 on some images, as I have read that ATWT does better with the larger scales, although I have noticed little difference with using MMT for all.
Good masks are critical to this process (and to noise reduction for the same reasons) as I like to apply stronger sharpening to the high SNR areas of the DSO, which is typically too much for stars and dimmer areas of the DSO. I generally use a luminance mask and use HT to crank up the brightness and crank down the background, usually 2-3 iterations in small steps. I then make a copy of the mask and use CloneStamp to get rid of the stars on one, and the DSO on the other.
I apply the DSO mask and are usually around these bias settings for most images:
1: 0 - 1 (lot of noise in layer 1, need to be careful)
2: 1
3: 0.025 - 0.050
4: 0.025
3 and 4 are really strong and need to be toned down on galaxies and nebula.
I then apply the luminance star mask and are usually around these settings:
1: 0 - 1
2: 1
3: 0.05
4: 0
Both 1 and 4 don't seem to have too much affect on the stars, but 2 and 3 will sharpen dimmer/brighter stars effectively.
For the DSO it is a dance between sharpening and noise reduction; I just keep playing with each until I achieve a balance that works for me. Sometimes I have to reopen the mask to fine tune it, reapply and resharpen / NR till I am happy. I use MMT for both sharpening and noise reduction, but always in separate steps.
Like I said, this works well for me, your results may vary. As with everything PI, trial and error is the key.
Joe
