Finally, the movements of your scope when you were taking the DSLR data was essentially random - that IS dithering.
I have to refute this every time it comes up. The movements of the scope are not dithering. If the scope moved enough to "dither" you would have stars trailing all over the place in the image. Dithering is not caused by movements of the scope.
Further, the drift of the stars across the frame due to imperfect polar alignment or differential flexure, which are also often called "dithering", are not only most definitely NOT dithering...they are the direct cause of the issue the OP is having: Correlated noise! (Walking noise, raining noise, etc.)
It IS the drift that ultimately allows the FPN to correlate. Once the frames are registered, the stars stop drifting...and now the pattern drifts. When stacked, it is the slight but consistent changes in the position of the pattern that ultimately "correlates" in the stack, giving rise to the streaking in the noise.
So, neither mount movements nor drift are dithering. Mount movements just couldn't be large enough (at a minimum, about 5 pixels, ideally around 10), as if they were then you would have severely blurred data. Drift is the fundamental cause of correlated noise in the first place, and if drift was large enough to "dither" by 5 pixels each frame, then you would have the obvious start of star trails.
The idea that there is any such thing as natural dithering is a myth. It has been repeated for years, but it is really not true. The only way to dither such that it can help you randomize the FPN in the registered subs so it averages out in the stack is to actually dither, using a program like PHD or a direct mount dither, and dither by 5-10 pixels every few frames for short (never less often than 3 frames, more often if the frames are longer), and dither RANDOMLY (do not use any kind of pattern dither, like box, or spiral, etc.)
Edited by Jon Rista, 15 December 2018 - 03:48 PM.