Rude Star Finder (2102-A)
"H.O. 2102 A / RUDE STAR FINDER AND IDENTIFIER / WITH
HYDROGRAPHIC MODIFICATIONS / AND SIDEREAL TIME CONVERTER / Letters Patent / No. 1401446 December 27, 1921 / No. 1919222 July 25, 1933 / Washington, D.C.: Published December 1932, at the Hydrographic Office, under the authority of the SECRETARY OF THE NAVY, SECOND EDITION, JANUARY 1934 / Price $7.50"
diameter 14 inches
Like the original Rude star finder, this one consists of cardboard planispheres of the northern and southern skies, each of which has a plastic meridian arm for determining the declination of the stars. Here, however, the rims of the planispheres are graduated to 3 minutes of time, and there are seven clear plastic altitude-azimuth templates for use at different latitudes up to 70o north and south. In addition, the planispheres rotate against a circle graduated to 365 parts, thus facilitating the comparison of civial and sidereal time. This feature was designed by Navy Captain Henry M. Jensen; John Edward Gingrich, a graduate of the Naval Academy who compiled Aerial and Marine Navigation Tables (New York, 1931) and who would later become a Rear Admiral; and Guillermo Medina, an engineer with the United States Hydrographic Office. The Hydrographic Office transferred this example to the Smithsonian in 1957.
Ref: G. T. Rude, "Star Finder and Identifier," U.S. patent
H. M. Jensen, J. E. Gingrich, and G. Medina, "Navigational
Instrument," U.S. patent #1,919,222.