Navigational Sextants

Navigational or navigation sextants are primarily used for celestial navigation. A navigational sextant is used to measure the angle of elevation of celestial bodies, usually the sun or moon, so that one's location and direction can be determined. More generally, a navigational sextant measures the angle between any two objects.



How does a navigation sextant operates?
Sextants are instruments that are used for navigating and surveying for maps. The user looks through an eyepiece, through which they can see the horizon and the reflection from the sky in the mirrors. If the second mirror on a moving arm is adjusted, the user can make a celestial body, such as a star, the sun or the moon appear to rest on the horizon as they look through the eyepiece. An angle in degrees can be read off the sextant and used to calculate lunar distance, longitude and where the ship is located on the Earth.

Popularity of navigational sextants
Sextants are instruments used by mariners to measure the angular distance between two objects (like the sun and the horizon). They are more accurate than astrolabes by having a telescope, mirrors, and a graduated arm. The mirrors allow seeing both objects simultaneously. When the computer crashes or there is no electricity, sailers must rely on this old-fashion instruments to guide them.

In modern navigation sextants, the light ray from the celestial body is reflected in two mirrors, one of which is adjustable and the other is half silvered. By the rotation of one mirror and its attached index bar, the body's image is brought down to the horizon. The rotation measures the altitude on the limb.