Dean Alva Ketelsen

1953 - 2023

DEAN A. KETELSEN (Dec. 16, 1953-Aug. 9, 2023), longtime resident of Tucson, died suddenly at his second home in St. Charles, IL of natural causes. He was 69 years old. Born in Clinton, IA to Alva & Janice Ketelsen, Dean grew up on a farm doing farmwork from a young age. In middle school, he received a small telescope as a Christmas gift, and fell in love with astronomy, thus determining the course of his life.He graduated from the University of Iowa (1976) with a BS in Physics & Astronomy, and worked at several local observatories as telescope operator, collecting data for scientific research. Over his lifetime, he contributed to many professional papers in astronomy and optics.After graduation, he moved (1980) to Tucson, but always retained his love for the Midwest. In Arizona, Dean worked first at Kitt Peak for the National Optical Astronomy Observatory (NOAO), operating the 4-meter Mayall telescope, then the largest in the Southwest. He also joined the Tucson Amateur Astronomy Association (to which he contributed in ways too numerous to count), serving as its president from 1991 to 1994.By 1984, Dean had begun working for the Optical Sciences Center at the University of Arizona (now the College of Optical Sciences) on the fabrication of large state-of-the-art astronomical telescope mirrors. Later in 1990, he transferred to the Steward Observatory Mirror Lab (continuing to work on very large telescopes), where he remained, full-time and later part-time, to the end of his life. At the Mirror Lab (now the Richard F. Caris Mirror Lab) he became a world expert on the fabrication of giant monolithic mirrors, contributing to the rebuilding of the MMT, and to the construction of the Magellan, Large Binocular, and Large Synoptic Survey Telescopes, some of the greatest instruments in use today.At heart, however, Dean always remained a passionate amateur astronomer, friend to countless other amateurs around the world. He belonged to numerous astronomy clubs and societies, and founded the present incarnation of the Grand Canyon Star Party in 1991 (which recently celebrated its 33rd anniversary) - an event that annually attracts thousands of visitors to witness the beauty of the heavens through telescopes.For many years, Dean was also an avid bicyclist, and rode in El Tour de Tucson, as well as the Des Moines "Register's Annual Great Bicycle Ride Across Iowa" (RAGBRAI). He retained his love of bicycling long after he ceased to be able himself to ride anymore. In addition, he was a great lover of cats. He and his beloved wives, Vicki Quave (d. 2003) and Melinda Johnson (d. 2016) were benefactors to many in Tucson.With Melinda too, Dean showed his deep love of the movies, attending the Loft Cinema in Tucson, streaming Turner Classic Movies at home (for "Golden Age" Hollywood classics), and making annual pilgrimages to Ebertfest in Champaign-Urbana, IL.He was an expert photographer, of the starry heavens, of nature in general, and of people. Many of his images have been published in books and magazines. He kept a blog (theketelsens.blogspot.com) and a Facebook page where many others can be found. He was tremendously generous with his knowledge, time, and equipment, helping countless amateur astronomers and photographers to improve their art. Asteroid 124075 Ketelsen is named in his honor.Dean is survived by his five siblings, and loved by numerous nieces and nephews from around the USA, as well as his many friends around the world. A Celebration of Life will be held for him on 1-Oct-2023, at 1:30 pm, in Room N210 at Steward Observatory (Univ. of AZ Campus). Donations in his name can be made to the Tucson Amateur Astronomy Association (www.tucsonastronomy.org), or to a no-kill animal shelter (or rescue) of your choice.