#8 SEXTANT
What is Sextant? The sextant is an instrument used to measure angles. Mainly used at sea, the tool is so named because its arc is one-sixth of a circle – 60 degrees. It adheres to the principle of double reflection hence it can measure angles up to 120 degrees. Practically speaking, the arc of the sextant is a little over 60 degrees and therefore the total angle measurable is about 130 degrees. Sextant is an essential tool for celestial navigation and is used to measure the angle between the horizon and a visible object (or two objects at sea. The sextant is used to measure the following: Vertical Sextant Angle (VSA) Horizontal Sextant Angle (HSA) Altitudes Principle of the Sextant 1. When a ray of light is reflected by a plane mirror, the angle of the incident ray is equal to the angle of the reflected ray, when the incident ray, reflected ray and the normal lie on the same plane 2. When a ray of light suffers two successive reflections in the same plane by two pla