Author(s): , ,
Institution(s): 1. Dark Sky Partners, L.L.C., 2. U.S. National Park Service
A large database of high resolution all-sky measurements of V-band night sky brightness at sites in U.S. National Parks and astronomical observatories is utilized to describe sky quality over a wide geographic area. Mosaics of photometrically calibrated V-band imagery are processed with a semi-automated procedure to reveal the effects of artificial sky glow through graphical presentation and numeric indicators of artificial sky brightness. Comparison with simpler methods such as the use of the Unihedron SQM and naked eye limiting magnitude reveal that areas near the horizon, which are not typically captured with single-channel measurements, contribute significantly to the indicators maximum vertical illuminance, maximum sky luminance, and average all-sky luminance. Distant sources of sky glow may represent future threats to areas of the sky nearer the zenith. Timely identification and quantification of these threats may allow mitigating strategies to be implemented.