(Editor’s note: DeeDee Wood is the owner of Black Cat Curiosities, an online antiques research and sales venue.)
Sailors and sea-faring voyagers have always had to find ways to measure where they were on the globe at any given time.
Through trial and error, many interesting nautical instruments were created to determine such important information.
The sextant was used for celestial navigation, and to determine an object’s altitude between the horizon and a celestial point, such as a star, to give latitude and longitude readings.
The sextant, unlike other nautical measuring instruments, measures the horizon, instead of the vessel’s position, in conjunction with a fixed point in the sky. 
Because the sextant does not require the user to remain perfectly still, since it is measuring the angle of the horizon compared to the fixed point in the sky, it was useful on ships due to the movement of the sea.
This is referred to as “taking a sight.”
The first sextant, in the form we know today, was made by an instrument maker in London named John Bird in 1757.
He also published two papers on methods of making astronomical instruments and are still referred to today for early examples of the methods for measuring nautical requirements with instruments.
The design of the instrument consists of an arc of a circle, which is marked off with increments of degrees. It has a pivot and an arm on a central circle, and a telescope mounted to framework.
The arm with a mounted mirror lines up with the telescope view and measures the angular distance of the stars, moon, or other celestial bodies to the horizon, in conjunction with measurements of the degrees on the arc.
Basically, with all of these readings from a fixed celestial body and the angle of the horizon give the navigator latitude and longitude.
Collecting nautical instruments in the antique world can swing from just buying an old nautical item to decorate an interior with a nautical theme, to restoration for use, to reselling of an item.
Many antique sextants were made out of brass, a staple of endurance for ship-worthy voyages, among other materials, such as ebony, ivory, decorative embellishments and a myriad of wooden boxes of all sorts that housed the instrument to protect it during voyages.
The really old, antique ones can be quite expensive in the marketplace, due to age and rarity of the piece.
Many useful and important nautical measurement instruments were made in the mariner’s attempt to measure their surroundings to give a geographic point on a map.
The sextant was a successful instrument due to the reliable angle measurement of the horizon with the fixed point in the sky.
The instrument has been modernized today to be a non-electric backup in ships and vessels, a reliable companion on the turbulent ocean, a constant from deep within the history of creating instruments that aid in nautical pursuits.
