This night had brought together nearly all the elements for my target picture: a lake far away from city lights and radio towers, one with no cabins or roads on the north while I had access from the south, a long night to contain a long exposure without the lake being already frozen, a stagnant high pressure center stalling the winds and keeping the lake surface at a mirror finish. And my schedule had allowed me to take a night away to make the shot! All these prerequisites had been met.
I set up my equipment and busied myself with other activities while the camera recorded the motion of the sky. A loud KERSPLASH startled me. Who would be throwing boulders into the lake in the middle of the night? I peered out onto the lake to see dark shadows swimming back and forth directly in front of my camera. Each traversal left a wake breaking up the reflected starlight. Occasionally a shadow would suddenly turn over end and dive, slapping its tail onto the water surface to make the boulder-throwing sound.
I cursed the beavers. They filled the night with constant gnawing sounds as they busied themselves around me. About halfway through the night I was startled again, this time by the sound of a tree crashing to the forest floor next to me. One more hazard to add to my list.
The picture I obtained was almost perfect, accented by the glow of the northern lights, and the intermittent breaks in the reflected trails as the beavers swam across the view, oblivious to my intent.