I shoot out of my shop quite a bit of the time off a shooting bench. Other day the tempture was in the mid 20's so I turned on my propane unit heater hanging from the ceiling about 30 ft behind me and blows warm air right on my bench mighty, comfy. When I looked throu my scope the heat waves made it impossible. I've looked across a hot desert on a 100 deg day, but this was like that on steroids. Made it impossable to shoot. Another lesson. At least this one was FREE!