This study presents results from computer calculations of the sky brightness due to proposed operations in the Rosemont Copper Mine (RCM) when viewed from six observation points, three of which are astronomically sensitive sites. The revised lighting plan for the RCM calls for a total of 6.4 million lumens. Our analysis shows that there would be an increase in sky glow at all sites due to RCM operations. At the astronomical observatory sites, including Fred L Whipple Observatory (FLWO), Jarnac, and Empire Ranch, the increase in brightness of the zenith is 0.4%, 0.7% and 1.1% respectively. In the astronomically "useful" portions of the sky, which we consider here to be out to zenith angle of 70°, the maximum brightening at these sites due to the proposed RCM lighting will be larger, reaching 3%, 8% and 10.5%, respectively.
Dark Sky Partners LLC. 2012. An Assessment of the Impact of Potential Mining Operations at the Rosemont Copper Mine on the Night Sky of Southern Arizona: II. The 2012 Lighting Plan. Prepared for SWCA Environmental Consultants. Tucson, AZ: Dark Sky Partners LLC. November.