The stars and arrangement of the heavens have always fascinated humankind. The journeys of ancient people could be navigated using the sun and stars. Both land and sea could be traversed using this navigation method. The navigation method of the stars and sun evolved, requiring both mathematical equations and constant measurement. Various instruments were invented for this purpose, and one of them was the sextant. Using a sextant, navigators could use their angle in relation to either the sun or the North Star, Polaris, to determine their exact latitude. With a sextant's measurements, navigators could pinpoint their exact latitude using the sun and North Star, Polaris, as anchoring points. Utilizing a sextant, the sun, and North Star, Polaris, navigators were able to determine their exact latitude on the earth's surface.
Civilizations with strong mathematician and astronomer populations were the first to promote the use of sextants. Astronomers and mathematicians were commonly one and the same. Though Arabs, Byzantines, and early Chinese had their own versions of the sextant, the Arabs were the very first, using their thumb and finger. The kamal, a square sextant with a cord, was developed later by the Arabs. The cord was a vital part of the kamal, as it allowed accurate determination of angles. The Silk Road allowed the kamal to travel through the ancient world, going as far east as China. Experimenting with different shapes and materials, such as bronze and mahogany, civilizations worked to create their own versions.
Popularized by the famously adapt ocean explorers, the Portuguese, the quadrant and its technology spread throughout the globe. Similar to the cord of the kamal, a string, called a plumb bob, was used in the bronze quadrant. The quadrant had two downfalls: the plumb bob would fly about in heavy sea winds, and keeping the quadrant perfectly vertical on a roiling ship's deck was difficult.
Closely resembling a Christian cross, the Dutch popularized a wooden sextant known as a cross-staff. The earlier letters of a Persian mathematician, however, reveal that Persia knew of the cross-staff, but that it had taken decades to reach Europe. Using a cross-staff commonly made the user look as though he were 'shooting the stars', hence the modern term 'to shoot for the stars'.
Walter Henshaw crafted the prototype of the modern sextant in 1711, known as the Davis quadrant. Created shortly thereafter, the sextant enabled navigators with a scale of 60 degrees. The first octant was made of mahogany, and allowed navigators 45 degrees of scale. Sextants were relatively easy to use, but octants required even less work. Octants replaced Davis quadrants as the archetypical navigation tool, while the sextant later replaced the octant.
Today, sextants are used as nautical decorations by many collectors, and are kept onboard most ships as a back-up navigational tool in case electrical GPS systems shut down. Sextants are rendered nearly useless, however, during cloudy or foggy times when the stars or sun cannot be seen. Sextants may prove more useful than machines, however, when equatorial or polar magnetism strikes a seafaring vessel. Modern sextants can be made of any material, though metal and heavy woods are preferred. Bright sun damages a navigator's ability, and shades are built into a sextant to prevent issues.