I read your article with interest since I'm looking for a dark sky site in AZ-NM and have looked at locations around Pie Town / Quemado. I agree that your SQM reading are un-good. "Far away from lights" one should see 21.8 or better. But I note that SQMs do differ. And Brian Skiff notes that when the summer Milky Way is overhead a zenith SQM reading at a dark site will be affected by the Milky Way. Might your varying readings from Sept 2007 be partly explained by when at night you made the readings? Milky Way moves ... I find that the major contribution to **perceived** sky brightness is atmospheric haze and "extinction". The "bowl of the sky" looks much much better when there is little or no horizon-fading. My absolutely best sky was observing from north Chile, in the Atacama desert at over 13000 feet. Retinal oxygen starvation did darken the sky, but what was scary-good was that the "color" of the sky was the same at the horizon as at the zenith. A setting star did not fade out. It just set, winking out past distant hills. Bob Ayers -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.