Waa???
Too techno for me. If you mean that stretching low S/N data yields a noisy result (= spiky histogram) well OK.
No, not "noisy". The spiky histogram is due to low bit depth data stretching to the point you can see each digital level. In the extreme, the image seems to have layers of stepped brightness. Stretching 32 bit files before conversion to 16 bit preserves signal level resolution ie spreads the signal over the available 16 bits.
I didn't think loading FITS RGB channels one at a time into PS from the same low S/N data would be noticeably better (??)
Well, it can be. Fits liberator cant import colour FIT files, so then it must be saved in colour TIFF to go direct in PS. If its not stretched 1st, then stretching in PS can cause the above artifacts. In this case FITs via Fits liberator pre-stretching could give a better result. I found that on saveing TIFFs in CCD stack as "scaled", clipping occured, so again, a worse result.
This is getting picy maybe, if the data is solid then the difference wouldnt be noticable.
I imagine you could also disrupt the colour balance you achieved in CCDStack thus making your PS exerience more challenging. Re the clipping, I'd suggest not doing any DDP or trying to adjust the gamma in CCDStack - much more control over these things in PS. I only do initial colour combination in CCDStack and save unscaled.
Yes, I dont do anything there either. Although many use DDP, and the advantage with it is its done in 32 bit, PS has more control with layer masks (and go-back history).
I import my LUM as FITS (logarithmic) into PS. Same with Ha but yes, I use a 10nm filter and my subs are usually 30 mins at the longer FL. I generally apply 2 to 4 stretching curves layers (depending on signal level). I then apply noise reduction to a masked copy of the unstretched layer. For my RGB I may apply more stretching layers and sometimes do noise reduction the same way. I typically also blur it a bit (but not always). Layer masking is a must of course.
Sounds like youve got that well sussed, yes I found layer masking a huge leap in image improvment.