I'm curious to find out what the average amateur astronomer's (on this forum) light pollution level at home is. I'm guessing that most people are like me and the majority of the time they are observing/imaging from their home.
My Bortle number is 3.6
My MPSAS number is 21
You should state where you obtained that data; I doubt that it came from your own observations. If you're obtaining it from a map or database, different sources often give very different data -- and none of them are likely to be a good match for your actual conditions.
For what it's worth, this is the first time I have ever seen a Bortle Class specified to a tenth; I'm not sure what that's supposed to mean. Conversely, it makes no sense to me to specify magnitude per square arcsecond to an accuracy less than a tenth. If you're rounding off, 21 could mean anywhere from 20.51 to 21.49, and there's a vast difference between 20.51 and 21.49!
As for my own readings, I rarely or never observe from my city home, because of the streetlights and obstructions. But my local city park is Bortle 8, perhaps trending toward 9, and I usually get SQM readings there between 17.5 and 18.0 in the early evening, perhaps a bit better after midnight.
My country home is Bortle 4 by most criteria, though it matches John Bortle's description of Class 5 better with respect to the zodiacal light. SQM readings on nights of typical good transparency range from about 20.7 in the early evening when there's snow on the ground to 21.4 in the small hours of the morning when the trees are fully leafed out.
Edited by Tony Flanders, 02 November 2020 - 05:59 AM.