I'm looking to get a SQM (Sky Quality Meter) and am wondering if anyone has a suggestion on a SQM that is affordable (I'm a teacher remember), is durable and provides accurate readings? I saw the Unihedron SQM (see the link below) and was thinking about that one. Any other suggestions? I want to use it to track conditions at some of the sites and parks I observe at here in Utah over time, probably a long period of time, and to see at which sites I get the darkest readings at. Thanks! Unihedron SQM