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Naval Meteorology and Oceanography Command U.S. Naval Observatory
Monday May 29, 2017

Home About History Instrument Shop Telescopes

Explanatory Material for the Six-inch Transit Circle
Prepared By the Astronomical Data Center

I/100A    Results of obs with the 6-inch transit circle (Hammond+ 1927-1982)
================================================================================
Washington 210, Results of observations with the six-inch transit circle
1909-1918
   Hammond J. C.
   Publ. U. S. Naval Obs. (2) 11, 665 (1927)

Washington 025, Results of observations with the six-inch transit circle
1925-1941
   Watts C. B., Adams A. N.
   Publ. U. S. Naval Obs. (2) 16, Part I, 1 (1949)

Washington 150, Results of observations with the six-inch transit circle
1925-1941
   Watts C. B., Adams A. N.
   Publ. U. S. Naval Obs. (2) 16, Part I, 255 (1949)

Washington 250, Results of observations with the six-inch transit circle
1941-1949
   Watts C. B., Scott F. P., Adams A. N.
   Publ. U. S. Naval Obs. (2) 16, Part III, 447 (1952)

Washington 350, Results of observations with the six-inch transit circle
1949-1956
   Adams A. N., Bestul S. M., Scott D. K.
   Publ. U. S. Naval Obs. (2) 19, Part I, 111 (1964)

Washington 450, Results of observations with the six-inch transit circle
1956-1962
   Adams A. N., Bestul S. M., Scott D. K.
   Publ. U. S. Naval Obs. (2) 19, Part II, 295 (1968)

Washington 550, Results of observations with the six-inch transit circle
1963-1971
   Hughes J. A., Scott D. K.
   Publ. U. S. Naval Obs. (2) 23, Part III, 165 (1982)
================================================================================
ADC_Keywords: Astrometric data; Fundamental catalog

Description:

This catalog is a compilation of seven catalogs of positions derived from observations with the six-inch transit circle of the U. S. Naval Observatory. The observations were obtained between 1911 and 1971 and were published in the catalogs: W210, W025, W150, W250, W350, W450, and W550. Proper motions and, in most catalogs, spectral types were added from other sources.

Introduction:

W210 contains the observations made with the six-inch transit circle of the U. S. Naval Observatory from May 1911 to August 16, 1918. The probable errors of a single observation in right ascensions range from 0.014s/cos(dec.) to 0.025s/cos(dec.). As expected, these are largest for the stars observed at low altitudes. In declination, the errors of a single observation range from 0.25" to 1.42" with only stars below altitude 15 deg. being greater than 0.6". The positions are reduced to the equinox 1910.0.

W025 contains the observations made with the six-inch transit circle of the U. S. Naval Observatory from 1930.3 to 1935.4 The probable errors of a single observation in right ascensions range from 0.012s/cos(dec.) to 0.023s/cos(dec.). As expected, these are largest for the stars observed at low altitudes. In declination, the errors of a single observation range from 0.30" to 0.52" with only stars below altitude 27deg. being greater than 0.37". The positions are reduced to the equinox 1925.0. The catalog also includes proper motions, primarily from the GC, reduced to 1925 and magnitudes and spectral types from the FK3, GC, or HD.

W150 contains the observations made with the six-inch transit circle of the U. S. Naval Observatory from 1936 to 1941. The probable errors of a single observation in right ascensions range from 0.012s/cos(dec.) to 0.024s/cos(dec.). Only stars observed below the pole or south of declination -25 deg. have probable errors greater than 0.016s/cos(dec.). In declination, the errors of a single observation range from 0.26" to 0.059" with only stars below altitude 27 deg. being greater than 0.35". The positions are reduced to the equinox 1950.0. The catalog also includes proper motions, primarily from the GC, reduced to 1950 and magnitudes and spectral types from the FK3, GC, or HD.

W250 contains the observations made with the six-inch transit circle of the U. S. Naval Observatory from 1941 to 1949. The positions were intended for reference stars for zone catalogs and the Lick proper motion survey. At least 75 stars/ sq. deg. were selected, uniformly spaced in right ascension with magnitudes in the range 5.5 to 8.5. Priority was given to stars with favorable observing histories. No double stars with separations in the range 1" to 10" were included. The probable errors of a single observation in right ascensions range from 0.12s/cos(dec.) to 0.21s/cos(dec.). As expected, these are largest for the stars observed at low altitudes with the probable errors greater than 0.16s/cos(dec.) only if the zenith distance was greater than 60 deg. In declination, the errors of a single observation range from 0.27" to 0.057" with only stars with zenith distances greater than 65 deg. being greater than 0.40". The positions are reduced to the equinox 1950.0.

W350 contains the observations made with the six-inch transit circle of the U. S. Naval Observatory from 1949 to 1956. A list of 255 Primary Reference Stars for Pluto was observed in February and March 1949. Seventy five stars per 100 square degrees between declinations +35 and +50 brighter than 8.5 mag. were included to provide a reference star grid for the Yale Photographic Zone Programs and the Lick Proper Motion Programs. Blaauw's O- and B-type stars and Cepheids were introduced in July 1954. The probable errors of a single observation in right ascensions range from 0.011s/cos(dec.) to 0.023s/cos(dec.) with only those below the pole greater than 0.015s/cos(dec.). In declination, the errors of a single observation range from 0.26" to 0.68" with only stars below the pole being greater than 0.4". The positions are reduced to the equinox 1950.0. The catalog also includes magnitudes and spectral types from the GC, HD or Leander McCormick Observatory Vol. XIII.

W450 contains the observations made with the six-inch transit circle of the U. S. Naval Observatory from January 1956 to September 1962. The probable errors of a single observation in right ascensions range from 0.011s/cos(dec.) to 0.023s/cos(dec.) with only those measured below the pole than 0.015s/cos(dec.). In declination, the errors of a single observation range from 0.21" to 0.54" with only stars measured below the pole being greater than 0.33". The positions are reduced to the equinox 1950.0. Stars north of declination -30 deg. were included but the emphasis was on stars north of -10 deg.

W550 contains the observations made with the six-inch transit circle of the U. S. Naval Observatory from March 1963 through December 1971. The primary observing list consisted of FK4 stars north of declination -31 deg., 1409 FK4 supplemental stars, and the northern portion of the Southern Reference Star program. Various other shorter groups of stars were added as the work progressed. The mean errors in right ascension range from 0.011s/cos(dec.) to 0.033s/cos(dec.) with only those south of declination -10 deg. greater than 0.015s/cos(dec.). In declination, the mean errors of a single observation range from 0.32" to 0.81" with only stars below declination -20 deg. or observed below the pole being greater than 0.4". The positions are reduced to the equinox 1950.0. The catalog also includes magnitudes and spectral types from various sources, particularly the GC and the Smithsonian Astrophysical Observatory Star Catalog (SAO).

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