M81

L: 167min
RGB: 40min

I added another half hour of luminance and re-processed M81.
Total: 2 hours 47 minutes of luminance and 40 minutes per color channel.

By the way, here’s a simple example of why astrophotographers chase faster optics, despite the more complex collimation and higher cost (not only for the primary mirror but also for correctors).
I calculated how much time it would take for a “typical” f/5 Newtonian to gather the same amount of light.

My setup: f/2.9 + Paracorr (1.15)
2.9 × 1.15 = 3.335
3.335 × 3.335 = 11.122225

“Typical” Newtonian: f/5
Using a standard corrector without reducing speed:
5 × 5 = 25

So:
25 / 11.122225 ≈ 2.24775

Considering only luminance, not color:
2 hours 47 minutes = 167 minutes
167 × 2.24775 ≈ 375.37 minutes

Result:
2 hours 47 minutes at f/3.335
equals about 6 hours 15 minutes at f/5.