Monthly Meeting

The making of large telescope mirrors has continued to evolve through the 20th century and is culminating in the activities of a couple different groups with distinctly different “styles”. In this talk, Dean Ketelsen will talk about the methods of the Richard F. Caris Mirror Lab (formerly the Steward Observatory Mirror Lab) at the University of Arizona. In particular, the “focus” will be on two distinctly different telescopes, the Large Synoptic Survey Telescope (now the Vera Rubin Telescope), and the Giant Magellan Telescope. The Lab’s efforts have revolved around making large substrates of 8.4 meters diameter (nearly 28 feet). He will discuss why the Mirror Lab has stayed with this method of fabrication and show why these telescopes are some of the most difficult large mirrors ever made. In addition, he hopes to reveal a “surprise” that almost anyone interested in astronomy will be excited about!

Dean Ketelsen is a Midwest native, former Iowa farm boy. He developed an interest in astronomy attending a 1-room country schoolhouse and obtained an undergraduate degree in Astronomy and Physics at the University of Iowa. Thanks to a work study job in the astronomy department there, Kitt Peak National Observatory came calling and he has been in AZ for 40+ years. Switching to optics after taking an “Optical Shop Practices” class at the Optical Sciences Center (U of AZ), he has worked on or supervised the crew making four 3.5 meter mirrors, six 6.5 meter mirrors, and six 8.4 meter mirrors. Since 2008 he retired to St Charles, IL, but still works part-time at the Lab as he splits time between the 2 locations. Now mostly a master optician emeritus, his job title remains “technical expert”!

The public is welcome to attend, free of charge.

This event is open to the public and free of charge.