The Tengfei GLH 130-40 Marine Navigational Sextant is a high-precision optical instrument used for celestial navigation. It is built to measure the vertical angle between a celestial body (like the sun or stars) and the horizon to determine a ship’s position.

The GLH 130-40 is particularly valued as a reliable backup for modern electronic GPS systems, as it functions entirely without external signals or power, save for its optional internal lighting.

GLH 130-40 Marine Navigational Sextant is a precise angle measuring instrument made of aluminum alloy. It mainly consists of the frame, optics, and angle-measuring device. The optics include a telescope, movable mirror, fixed mirror, and filters. The angle measuring device includes a graduated arc, index arm, drum wheel, and vernier scale. These components are all mounted on the frame and connected into a whole by the index arm. The sextant measures angles based on geometric principles such as “the sum of the exterior angles of a triangle is equal to the sum of the two non-adjacent interior angles,” “corresponding angles formed by parallel lines are equal,” and “the central angle can be measured by the arc it subtends.” PREFIX = O