Sextant by Georges Derrien and Yves le Prieur, France

sextant

Vernier sextant, brass frame, brass fittings, wooden handle, with artificial gyroscopic horizon. Dated ca 1920. Has cross hair telescope, no sun filters. On back of horizon mirrors "Gyrosextant Bonneau/ Derrien & LePrieur". Graduation from 90°-0° in real degrees. Not very successful attempt to manufacture a sextant that could be used when the horizon was not visible. The gyro is located in the cylindrical container and was supposed to give a stabilized horizontal reference. Engraved on the scale ‘La Precision Moderne Paris 2306’. ‘Georges Derrien, Lieutenant de Vaisseau de reserve (reserve lieutenant in the French Navy) seems to be the inventor, ‘Yves le Prieur, directeur technique de la société la précision moderne, 78 rue d’Anjou Central 19-29’ seems to be the manufacturer. See Peter Ifland, Taking the Stars. Celestial Navigation from Argonauts to Astronauts. (Malabar, 1998) pp.161-162.]