Located 56 miles southwest of Tucson via State Route 86. Allow 90 minutes of drive time from Tucson. Take I-10 to I-19 south. In less than one mile take the Ajo Way/Hwy 86 exit 99. The observatory houses the world’s largest collection of ground-based optical telescopes, conducts research in astronomy, and monitors the sun and stars. There are 3 tours daily lasting 1 hour. The Nightly Observing Program is available by reservation only and an admission fee is charged.