Sextant - Hemisferium
This instrument is really a reproduction of an Octant of the mid 17th century.
By semi-accurately measuring the height of stars or the sun, the Octant allows navigants to determine geographic latitude.
In 1731 John Hadley (England) and Thomas Godfrey (Philadelfia, U.S.A.), demonstrated the Octand, independently.
The arc of an Octant is 45º or 1/8 of a circle (hence its name) and is divided into 90 parts each ½ degree. The Sextant (1757) replaced the wood frame with metal, progressively tooks Octant´s place and is still used today.