October 20, 2020

Twilight

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 […]
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October 20, 2020

The marine sextant

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 […]
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October 20, 2020

Uses of the sextant

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). […]
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October 20, 2020

Parts of the sextant

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 […]
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