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Naval Meteorology and Oceanography Command U.S. Naval Observatory
Sunday June 25, 2017

Home About History Instrument Shop Telescopes

USNO Six-inch Transit Circle

The 6-inch Transit Circle was in operation for over 100 years, observing stars and solar system objects fundamentally from the same location in Washington, DC. It is now retired. The instrument measured the "constants" of azimuth, collimation and nadir and level and made observations of the Sun and planets. The fundamental azimuth is determined from observations of circumpolar stars. Below are listed some of the star catalogs derived using observations from this instrument. A brief explanation of each catalog has been provided by the Astronomical Data Center.

The star catalogs observed with this instrument are available here (right click to download):

1.W2102499 stars
2.W0252383 stars
3.W1501536 stars
4.W2505216 stars
5.W3505965 stars
6.W4502685 stars
7.W5504916 stars
8.W1J00 7267 stars

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