The sextant, a reflection instrument derived from the octant, consists of an arc of a circle of about 60 degrees. It is used to measure the altitude of the Sun or a celestial body above the horizon at sea. It was sometimes used on land as well, to determine the angular distance between two points. A mobile arm carrying a mirror and pivoting on a graduated arc provides a reflected image of the celestial body overlapping the image of the horizon, which is observed directly. The desired angle is read directly on the scale through an eyepiece. This highly compact model was also suitable for travelers who liked to take bearings on deck. Made by Louis-Félix Védy firm.