Instruments for measuring the height of the stars were in use before the discovery of the method for identifying longitude through the coordinated measurement of the stars and the on-board clock. However, this discovery reinforced the need for instruments of ever greater precision and greater skilll  in the officer's ability to read it correctly.
Octants were complex instruments and required skill and experience. They did not easily establish themselves in Italy: they were very expensive and captains often bought them abroad and second-hand. As personal property of the naval officer, they were often passed from father to son, so that it is sometimes possible to reconstruct the history of the owners. The octant exhibited is the most precious of the collection, also thanks to the information that allows us to trace its full history.