Evolution of Tucson city lights, 1959 to 2003. These three images, taken in 1959, 1980 and 2003, show the evolutionary change and growth of the artificial lights emitted by the greater Tucson area as seen from Kitt Peak National Observatory (KPNO), about 90 kilometres southwest of the central urban area. Although the light emission has grown, light pollution control measures has limited stray light to the extent that KPNO remains a world-class astronomical site.