I am very skeptical horses or even small campfire smoke can be seen at 15 miles.... I will take the word of anyone who obtained permission and visited the crows nest as to whether this feat was possible.
Yeah, it's possible. I've been there. First of all, it wasn't 15 miles, though that's close. Crow's Nest hill is about 1 mile from the divide... a little less. Then it is 11.81 miles from the top of the divide-- not straight line-- to Ford A. The village was about 3 miles from Ford A, but angled from the Crow's Nest, so the difference-- straight-line-- would be a little shorter. I can measure it exactly if you want.
The problem was the bluffs would obscure anything that far downriver, so you couldn't possibly see the village, other than by rising smoke, which is what was reported. The pony herd was probably as large as 20,000 horse, but in multiple sections. That is what was described as moving worms. Binoculars picked up 1 1/2 tepees about 10 miles away, so there were enough signs that something was there.
The interesting thing about it is Custer's supposed second trip. I have a fairly good idea what happened and what that little controversy was, but I prefer not to reveal it at this time. Varnum adamantly denied any such trip to the Crow's Nest... and I believe him.
Best wishes, Fred.
That's because it wasn't to the Crow's Nest.
“who wishes to fight must first count the cost”
― Sun Tzu, The Art of War