[AZ-Observing] My NM Lot SQM Readings

I just got back from my NM lot last night. While there (about 34 degrees 
0.929' latitude and 108 degrees 7.91' longitude) I got some SQM readings 
on the nights that were clear. All are an average of 3 or more readings.
Sept 13-14
     9:10pm  21.75
    10:05pm  21.70
    11:05pm  21.65
     2:50am  21.84
Sept 15
     9:40pm  21.61
    10:55pm  21.54
Sept 17-18
    11:05pm  21.42
     3:55am  21.54
Sept 18-19
    11:15pm  21.54
     2:30am  21.59

I see a trend downward as the Moon increases in phase. Even though it 
would seem the Moon should have been set long enough to not affect the 
readings, this is the only thing I can see that could explain the drop 
in readings from Sept 13-14. Also, early in the evenings the Milky Way 
is at the zenith and I have discovered that it has a slight effect on 
lowering the SQM readings. I believe at 2:50am the sky is not as near 
lit up from stars compared to early evening. This, plus a Moon closer to 
a new Moon may explain the Sept 13-14 reading of 21.84.

The only SQM reading I have at my place in Dewey, Az is 21.14 on August 
8th. Pogson's scale is
F1/F2 = 100exp(1/5*(M2-M1)), F=flux  M=magnitude
Using this scale to calculate how much more brighter in terms of flux my 
Dewey place is compared to the best reading of 21.84 at my NM lot I get 
a flux ratio of 1.91. In other words, my Dewey lot has 91% more light, 
as a flux reading, than the NM lot due to light pollution. Even though 
91% is a big increase, I do not know if this would have a significant 
impact on integration time doing imaging or spectroscopy, given that the 
SQM magnitude of 21.14 at my Dewey place is not too bad.

I am thinking of making another trip to my NM lot the second weekend in 
October. If anyone might be interested in knowing what the skies are 
like bordering The Plains of San Augustin and bordering the Very Large 
Array, observing at my place would be one way to find out. If anyone 
would like to join me on that weekend let me know and I will provide 
directions on getting there.
Stan



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