After the recent breakthrough, and thanks to some precious help by Giancarlo Calzetta, I was finally able to tame the bulk of the problem.
What’s left is some differential flexure, at least when imaging west. In the meantime, I was able to produce this quick jab at M13 (thanks Samuel for the RGB data!)
The image could be better focused (I messed with the focuser when I was in Nerpio, but it’s fine now) and the RGB data is not calibrated, so if you zoom in you can see lots of colored hot pixels. I’m still happy I can see the end of the tunnel.