Hi Steve,
for assessing a potential site try
lightpollutionmap.info here...
https://www.lightpollutionmap.info/#...FFFTFFFFFFFFFF
Type in the location/suburb/country you want and select from what comes up, then zoom around the map even at street level to pin point an area of interest. If you use the World Atlas 2015 overlay (in the panel on the top right), when you click on a particular location the sky brightness (in µcd/m^2, or mcd/m^2) data are reported and SQM value is reported. If you use the VIIRS data you can get more current years, but it is reported in less intuitive sky radiance terms.
Best
JA