Photo by David Friend Productions, San Diego, California
NAVIS-AZIMUT COMPASS CORRECTING AZIMUTH CIRCLE by F.W. GLEERUP & P.M. SORENSON
05-003. Swedish, after 1895, signed on top "NAVIS-AZIMUT" and in script "F.W. Gleerup, Stockholm, P.M. Sorenson." Made of polished brass, 15 3/4" tall on its 12 5/8" x 10 1/4" base, with 7 7/8" diameter turntable. The upper ring features two sighting vanes that serve as an alidade and is graduated in north and south declinations, divided to a.m. and p.m. The lower ring is graduated from 0 to 90 degrees for both north and south latitudes. The turntable (internally gimballed) is graduated from 0 to 360 degrees, as on a bearing circle, and rotates with flywheel ease. Included with the instrument is the original 20 page booklet (French edition) with description and instructions written by Gleerup and testimonials from leading naval figures of Europe. The massive all brass construction and elegant machining work, typical of Sorensen's work for the Royal Academy, were likely far too expensive for successful competitive marketing of the intrument, which empodies all of the characteristics of a fine hand made instrument and none of those typical of "production" nautical items.
P.M. Sorensen was the chief instrument maker to the Royal Swedish Academy of Sciences in the last decades of the 19th century. This compass correcting azimuth circle was designed by the Swedish mariner Captain F.W. Gleerup to take celestial observations to check for deviation of a ship's magnetic compass. Sorenson created a number of unique instruments for the Uppsala Astronomical Observatory, including a spectrograph commissioned by Niels Duner in 1897. Examples of Sorensen's instruments can be found in museum collections, including an identical example of this "Esinekokoelmat" in the Merimuseo Nautical Museum in Finland (http://www.rmm.fi/kavijan_info/esinekokoelma11.htm).
