Did mountain men use anything like a binocular?

[Brokennock]

So how long do our proponents think our fantasy spyglass would have actually lasted in the Rocky Mountains during this period? Given packaging and transport options of the time,,, and carrying it in a manner that it would be useful.....

Could they gave seen a riverboat captain or military officer using one and thought it was great? Of course! No one is saying these situations weren't possible, or even probable.

Spend my hard earned trapping money on something fragile that I have to take special care of, considering my rifle of the time is delicate compared to a military arm of the time or one of today's unmentionable, so I already need to care for that.....
No, I'll pass on that and carry more powder, maybe more pemmican, or some extra little trinkets as trade items and peace offerings for the natives.

 

[Brokennock]

For an individual on his own, (free trapper, how many were there?) a "spyglass" would be more useful but still more or less an unnecessary burden.