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Henry L. Giclas (1910–2007)

Published onDec 01, 2012
Henry L. Giclas (1910–2007)

Lowell Observatory astronomer Henry Lee Giclas died of a stroke 2 April 2007 in Flagstaff, Arizona, where he was born 9 December 1910 and lived nearly all of his 96 years. He is best known for a lengthy survey of proper motions of stars and the discovery of a number of asteroids and comets.

Giclas was the only child of Eli Giclas, a son of French immigrants (original spelling Gicquelais) and Hedwig Leissling Giclas, an immigrant from Berlin, Germany. Eli Giclas was an engineer who came to Flagstaff in about 1907 to establish a system to provide water for the Santa Fe Railroad. He later worked for the local lumber company and became the first water superintendent for the city. He helped in the installation of the 42-inch reflecting telescope at the Lowell Observatory in 1909–1910.

Young Henry grew up around the Observatory, which is on Mars Hill overlooking Flagstaff. After high school he studied one year in Flagstaff at what is now Northern Arizona University and then transferred to the University of Southern California to study engineering. He returned to Flagstaff in the summer of 1930 and helped out as a volunteer at Lowell. The following year he left USC after becoming ill and returned to Flagstaff again. He was hired by Director V.M. Slipher as a “general assistant” at the Lowell Observatory in September 1931.

As an assistant Giclas helped out with such tasks as experimenting with dyes for Slipher, mending equipment, and taking photographic plates, including objective prism spectra, for some of the astronomers. He helped Carl Otto Lampland reduce plates to determine the position of the asteroid Eros, using mechanical calculating machines. In between he spent the academic years 1933–1935 in Tucson, completing most of the work for his bachelor’s degree in astronomy at the University of Arizona, but the degree was not awarded until he completed a last course in absentia in 1937. He took a leave in 1941–1942 to do graduate work in astronomy at the University of California at Berkeley, and after returning to Flagstaff was promoted to astronomer. Although he did not complete a Ph.D., he was awarded an honorary Doctor of Science degree from Northern Arizona University in 1980. In 1936 he married Bernice Kent, who had been a secretary at the Observatory and a high school teacher. Their only child, Henry “Hank” Giclas, Jr., was born the following year. Bernice died in 2003.

During the 1930s Giclas, working under Carl Otto Lampland, made many measurements of positions of asteroids and comets, some of them on the plates taken by Clyde William Tombaugh in his search for additional planets. He continued to photograph and measure positions of minor planets and comets throughout his career, usually assisted by Mary Lou Kantz, and he often provided positions of newly-discovered comets to those, especially Leland Erskin Cunningham of the University of California at Berkeley, who wished to calculate their orbits. He discovered several comets, including periodic comet 84P/Giclas, and some eighteen asteroids, including a few whose orbits take them near Earth. In 1949–1954 he and Robert Howle Hardie searched for solar variation by making photometric observations of Uranus and Neptune.

Giclas made use of his engineering background in such tasks as site surveys for locating new telescopes, designing new sites, and designing and erecting domes for new telescopes. From about 1952 to 1974 he served as executive secretary of the observatory, taking over the administrative work and bookkeeping.

Tombaugh had photographed the entire sky visible from Flagstaff with a 13-inch refractor from 1929 to 1945, making his most famous find, Pluto, early in the search. It became clear that if the survey were repeated after some years the two sets of plates could be “blinked” and proper motions determined for vast numbers of stars. This became Henry Giclas’s most important work. He supervised the Lowell proper motion survey of the northern hemisphere from 1957 to 1971, when the catalogue of 8991 stars with proper motions greater than 0.26 arc seconds per year was published in the Lowell Observatory Bulletin. Most of the blinking was done by Robert Burnham, Jr. (who wrote and self-published his famous Burnham’s Celestial Handbook during this period) and Norman Gene Thomas. The same telescope was used and plates 14 x 17 inches each covering 11.5 x 14 degrees were made. Giclas used these plates to discover about 1500 white dwarf candidates and also photographed a subset of the faint proper-motion objects with the 72-inch Perkins reflector.

Giclas and his team then extended the proper motion survey to that portion of the southern sky visible from Flagstaff, publishing this work in 1979. By then more years had elapsed since Tombaugh’s first-epoch plates had been taken, and they were able to measure proper motions as small as 0."20 per year. Although he officially retired in 1979, Giclas kept his office at Lowell—and used it nearly every day—until 2006, when he was 95. In his later years he wrote a lengthy set of reminiscences, practically a history of Lowell Observatory from 1930, and did fund-raising for the Observatory. Lowell’s sole trustee, William Lowell Putnam, was quoted as saying, “Whenever any us wanted to know anything about the history of this place, we’d say, ‘Go ask Henry.’” Unlike many of his colleagues, who remained on Mars Hill, he and his family lived in the town of Flagstaff from 1953, and he was greatly liked and esteemed in the community. He met with and drank with the leaders; he served on the water board and as president of the Northern Arizona Pioneer Historical Society; he was active in the Elks Club; and for decades he met regularly with a group of local citizens for breakfast. He served as an adjunct professor at Northern Arizona University from 1972 to 1990. Both he, in 1977, and Bernice, six years earlier, were honored by the local newspaper as Citizen of the Year. Asteroid (1741) Giclas was named in his honor by its Indiana University discoverers.

Photo credit: Lowell Observatory Archives

External links: Oral history interview conducted by Susan Louise Rogers, 4 December 1975. Flagstaff City-Coconino County Public Library Oral History Project, 1975–1977. Sound recording and transcript available at

Oral history interview conducted by Robert W. Smith, 12 August 1987. Niels Bohr Library & Archives, American Institute of Physics, College Park, MD, USA. Transcript available at

Bruner, Betsey. “Like a Fading Star, Flagstaff Astronomer Giclas Dies at 96.” Arizona Daily Sun, 2 April 2007.

Author information: Joseph S. Tenn, based on his biographical note for the Biographical Encyclopedia of Astronomers (Thomas Hockey, ed.; Springer publishers)

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