Dark Spots/Speckles

[SeattleStarGazer]

Hi and Happy Holidays! I'm fairly new to PI and have been following the online tutorials and Warren Keller's book to learn. I've typically do nebulae (Rosette and Horsehead specifically) and following workflow of the background extraction. neutralization, noise reduction with MLT, stretching with HT, TGVnoise, sharpening with MLT and Unsharp Mask, Morphological Transformation, LocalHistogram etc. I've noticed my images developing what looks like small dark spatter spots (like you took a wet brush and shook it at the image). These are typically a few pixels in size. I figure I'm overprocessing somehow but there doesn't seem to be specific spot (pun not intended) where they suddenly appear, just get more noticeable. Any ideas?

I'm attaching a greatly zoomed portion of the HH where they are obvious.

[Warhen]

Hey Seattle, I think we'd be better able to offer suggestions if we could see what the background looks like before any NR, then after MLT, and again after TGVD. Maybe less zoomed-in. Are you shooting OSC or Mono? If Lum is available, that might be best. Something I ran into myself was letting too much dark noise through integration. That noise ended up looking splotchier than nice Gaussian salt and pepper noise to start with, and only got worse through smoothing. MMT linearly can be prone to splotchy/mottling as can TGVD in the linear (not nonlinear) but it doesn't sound like you're doing either of these. So, my guess is beginning with too much dark noise, and or too heavy MLT and/or less than ideal TGVD settings. Repost something a bit more illustrative if you like.