I've got some real world info from this evening. I just got back in from hunting. Didn't see much till just about time that I could see little with my eyes. I grabbed the Leica binocs to scan the woodline one more time. There was a coyote way out at the far edge. That's about 400 yards. He started zigzagging in my general direction. It was pretty darn dark by then and I kept losing him in the binocs. Then..there he was out in the middle of the hay field in some dry brown grass. I could see him pretty well with the binocs, but I did worry that I wouldn't be able to find him in the scope (Leupold VariX-III 4.5-14x40). I made a mental note that the coyote was sitting just left of the round bale directly in front of me, so I pulled up the rifle, dialed the scope to about 5 power, found him in the crosshairs (and he was as clear as he had been in the binocs, and by that I mean that I could see him and determine which end was tail and which was head). The muzzle flash was very bright.
The point of all this is that my scope is not the latest generation, but I could see the coyote fairly clearly at well past legal shooting time.