Ray, you are far from being a pest. This is interesting and informative!
I just did some unity gain subs. Background sky is
~300ADU @ 60sec exposure
~600ADU @ 120sec
~1200ADU @ 240sec
I'm guessing my sky Bortle scale is about 5 by that description.
https://www.lightpollutionmap.info says I'm a yellow zone, SQM 20.4-20.9. And we have a few nasty sodium lights in front of our house, although the backyard is shaded from it. I'd like to take them out!