Since 1991, Ketelsen has organized the Grand Canyon Star Party, which has allowed tens of thousands of canyon visitors to better appreciate the night sky. Every year he organizes the "Star Party for 55,000" at a University of Arizona home football game. During this event, Ketelsen and Tucson area amateur astronomers set up telescopes outside the football stadium and give incoming fans views of astronomical objects. Among his many other astronomy activities, he has worked as a volunteer for the ASP's Project ASTRO, bringing the wonders of astronomy into Tucson classrooms. He is currently a Senior Research Specialist in the Steward Observatory's Mirror Lab in Tucson.
