Starman over on Cloudy Nights has put up a comparative reference of SQM reading and light pollution map colours. The thread is here, check Starman's entry down the page:
http://www.cloudynights.com/topic/49...2#entry6558839
Extract is here:
"From correlating colors on the LP map (even the new one, with 15 shades) to wide SQM readings, I get the following:
Green zone 20.9-21.1
Dark Green zone 21.1-21.35
Blue zone 21.35-21.5
Dark blue zone 21.5-21.6
Light gray zone 21.6-21.7
dark gray zone 21.7-21.8
black zone--we (USA) don't have any black zones."
My personal SQM readings are supportive of Starman's conclusions, based on the Australian light pollution map.
I live in a Green Zone and can achieve readings near 21 in good conditions. Bretti NSW a dark gray zone, returns 21.77 on a regular basis during new moon periods; likewise Chaffey Dam is in the same reading category.
Does this correlation stand up to your experience?
Light pollution map is located here:
http://www.lightpollutionmap.info/#z...ayers=B0TFFFTT
Just move it around (and zoom in or out) to locate your area.