Just a thought, if you have a smart phone, use the compass on it and pick up a smart phone holder for either the dash or window mount. I use the compass on my IPhone4S to zero in my Direct TV dish, it is amazingly accurate and easy to read.
Don't have a compass on your smart phone, well your only an app away.
2013 Ford F350 FX4 4x4 PSD
2013 Wildcat 353LS
2015 Day/Nights Camped 5
2014 Day/Nights Camped 29