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Naval Meteorology and Oceanography Command U.S. Naval Observatory
Wednesday August 23, 2017

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Astrometry Department History

The Astrometry Department has existed in various forms since the 19th century. For much of its history its main concern has been the operation of transit circles. In the late 1950's two departments, the six-inch transit circle and the seven-inch transit circle divisions, were responsible for the operation of the two instruments and the data analysis and production of the observational catalogs. The Equatorial Division operated the 26- inch refractor, mostly for double star research. In 1969 the seven- inch transit circle was sent to El Leoncito, Argentina to observe the southern component of the International Reference Stars, the SRS. The six-inch transit circle observed the northern component of the IRS, the AGK3. At the time the names of the divisions were changed to Northern and Southern Transit Circle Divisions. In 1977 the seven-inch transit circle was returned to Washington where an image dissector micrometer system was developed and installed. The two Divisions were combined with the Equatorial Division to produce the Astrometry Department. The seven-inch transit circle was sent to Black Birch, New Zealand, to observe the second epoch of the SRS, while the six-inch transit circle observed the IRS in the North. An 8-inch twin (yellow and blue lens) astrograph was acquired and sent to Black Birch to photograph the southern sky. These projects ended in 1995 and the seven-inch transit circle was removed from Black Birch and placed in storage in Washington. The six-inch transit circle remains operational (and celebrated 100 years of operation in 1997 with a brief set of measurements made by T. Rafferty), but the successful operation of the European Hipparcos satellite effectively obsoleted the transit circles.

In 1997 the astrograph mentioned above was fitted with a new "red" lens and a 4kx4k CCD camera and sent to Cerro Tololo, Chile to begin a program of observing the southern sky to unprecedented accuracy from the ground.

6-inch Transit Circle
DirectorTenure fromTenure to
J. C. Hammond 1911 December 31, 1933
C. B. Watts 1934 1959
A. Norwood Adams 1959 1969
Benny L. Klock 1969 1976*
* see Transit Circle Division below.

9-inch Transit Circle
DirectorTenure fromTenure to
A. N. Skinner 1894 1900
F. B. Littell July 30, 1901 September 3, 1903
W. S. Eichelberger September 3, 1903 September 30, 1908
F. B. Littell October 1, 1908 November 11, 1913
H. R. Morgan November 11, 1913 1944**
** the 9-inch Transit Circle Division was decommissioned at Morgan's retirement in 1944

7-inch Transit Circle
DirectorTenure fromTenure to
Francis P. Scott 1948 June 12, 1970
Jack L. Schombert 1970 1976***
*** see Transit Circle Division below

In 1977 the transit circle instruments were placed under a single Transit Circle Division.

Transit Circle Division
DirectorTenure fromTenure to
Jack L. Schombert 1976 1977
James A. Hughes 1977 1982

In 1982 the Transit Circle Division became the Astrometry Department.

Astrometry Department
DirectorTenure fromTenure to
James Hughes 1982 Jan. 15, 1992
F. Stephen Gauss May 9, 1993 June 2,2000
Theodore J. Rafferty October 8, 2000 June 15, 2002
Ralph A. Gaume June 16, 2002 present

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