Table 4. Results of fitting a Gaussian function to the differences between observed SQM values and those expected based on the sky luminance expected using the World Atlas for that location. The “2012 all” dataset was not normally distributed, as is indicated by the poor χ²/dof, and the standard error in this case is larger than σ.

Dataset	Observations	Mean	Fit σ	χ2/dof
2009–2011	1130	0.01	0.35	23.4/19
2012 all*	771	0.13*	0.33*	67.3/16
2012 excl	605	0.02	0.35	19.3/16
2009–2012	1735	0.01	0.37	21.0/23