The sextant is made up of the following parts: The frame. The handle. The telescope or monocle. The rising piece. The arc. The index arm. The clamp. The worm and rack. The micrometer drum. The micrometervernier. Electric light. The index mirror. The index mirror clips. The index mirror (first) adjustment…
Although the marine sextant is seldom used these days due to the introduction of satellite navigation systems (ie GPS), it still can be used for the following: Measuring the altitude of the stars, sun, moon and planets in order to determine geographical position out of sight of land (ocean navigation).…
Introduction. The marine sextant is a precision built optical instrument f which is used to measure altitudes and angles. It used to be an essential part of a ship’s navigation equipment. The sextant got its name from the fact that the length of its graduated arc is approximately one sixth…
Explanation of twilight. Twilight is the period of approximately one hour’s duration before the sun rises in the morning and the period of approximately one hour’s duration after the sun sets in the evening, ie between the times when the sun is 12° below the horizon and sunrise in the…
Calculating times of sunrise and sunset. The times of the visible rising and setting of the sun are contained in the daily pages of the nautical almanac. They are tabulated for the middle day of the three on that page and provide the Local Mean Time (LMT) of the rising/setting…
Polar Distance. This is the angular distance of a body from the elevated pole (the pole that is above the celestial horizon). This is the distance PX in the sketch. When the elevated pole and the declination have the same names, the polar distance is 90° – declination. When they…