Using a Sextant

sextant is an instrument generally used to measure the altitude of a celestial object above the horizon. Making this measurement is known as sighting the object, shooting the object, or taking a sight. The angle, and the time when it was measured, can be used to calculate a position line on a nautical or aeronautical chart. A common use of the sextant is to sight the sun at noon to find one’s latitude. Held horizontally, the sextant can be used to measure the angle between any two objects, such as between two lighthouses, which will, similarly, allow for calculation of a line of position on a chart.

Celestial navigation continues to be used by private yachtsmen, and particularly by long-distance cruising yachts around the world. For small cruising boat crews, celestial navigation is generally considered an essential skill when venturing beyond visual range of land. Although GPS (Global Positioning System) technology is reliable, offshore yachtsmen use celestial navigation as either a primary navigational tool or as a backup.

using sextant

Wikipedia contributors, “Sextant,” Wikipedia, The Free Encyclopedia,

Historical Interest



Learning Celestial Navigation

Hawaii by Sextant


General Navigation

The Nautical Sextant


One thought on “Using a Sextant

  1. Jack D. Cussen says:

    This is a very interesting device and it’s too bad more people have no idea what it is used for. Lots of people don’t realize that a mathematical analysis can be made of this instrument that can explain its
    usefulness. Unfortunately, this is not a new phenomenon but it appears to me that not much progress is being made to improve this. Recently, I came across an article that stated the United States is slipping in our reasoning ability. I feel that high school students need far more hands on exposure to devices such as this than they are now getting. I taught high school physics for eight years and I speak from experience. Thanks for this opportunity.

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