I’ve got a basic old HEQ5 (just stepped motors) that I can get 2-3 minutes at 10”/pixel. The issue here is the periodic error, at 3 minutes it is about half a worm cycle. My EQ6 has lower PE than my HEQ5 as it’s had numerous upgrades so it could probably do near indefinitely at 10”/pixel; 85mm lens with a 24MP APS-C with no anti-aliasing filter.
Of course if I used my D700 with a 300-500mm lens it would probably get the same results because it’s pixles are huge and it has blurring filters that make it very user friendly
