Located atop the 6,875-foot summit of Kitt Peak, the observatory offers nightly viewing and an advanced overnight program that lets visitors stay on site, use advanced equipment and "explore some of North America's most spectacular night skies." (Stargazing by reservation only.) Open from 9 a.m. to 4 p.m., daily. Guided tours are at 10 a.m., 11:30 a.m. and 1:30 p.m.; a single tour is $5.75, $3 age 7 to 12, free younger child, June through October; $7.75, $4 age 7 to 12, free younger child, November through May. Special rates for three tours are available. Night tours feature four hours of guided observing time and a box dinner; $49, $45 student, military or senior. Call 318-8726, or visit noao.edu/kpno for more information.