I've noticed this for the last two years. It used to be worse, where I needed to re-align after 20 or 30 frames.
Now I still need two after 60-80 frames. The drift is certainly there (with as low as 2 pixel dithering every 4 exposures).
I currently use a wide FOV (348mm F/L) but I know once I jump to a narrow FOV this will be a serious issue.

Peter

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