Yes, I think it's a rain gauge. The standard National Weather Service rain gauge is basically a funnel in a bucket, 20 cm in diameter and 50cm high. This is placed on some kind of base (a wooden bench in the photo?) such that the top is between 3 and 5 feet off the ground.
The weather service has been keeping precipitation records at Cumbres since the early 1900s at least, and I understand it has or used to have the highest average annual precipitation of any weather station in Colorado, 36.4 inches. (Obviously most of that would actually be snow rather than rain.)
-Philip Marshall