Old Navigational Instruments



The Sextant is the most well known navigational instrument in the world and still in use to this very day.




 

Navigation is the art of getting from one place to another.
The first records of boats large enough to carry trading goods are from between 3500 B.C. to 3000 B.C., so we can safely assume that that time also marked the beginning of navigation. These first navigators had no choice but stay close to shore and navigated by sight of landmarks or other characteristics on land that they could see. They travelled mostly by day and went for a safe harbour to stay at anchor at night. They did however develope kind of rudimentary charts, which listed directions, showed crude drawings depicting landmarks and certain dangerous places like reefs, sandbanks or rocks in the water.

Early documents state that the more experienced mariners of the time were said to plot their course by using certain star constellations so most vessels followed the east/west movement of the sun or the track of the stars. However, the ancient navigator had no way to accurately determine longitude and therefore, once out of sight of land, had no idea how far east or west he was. So his estimates were made based upon the time it took to sail from A to B. This is the simplest form of navigation and it is called dead-reckoning; it is still used by navigators today.

To determine the distance travelled from one point to another, the navigator would multiply the time he sailed by the speed of the vessel. Of course these crude calculations were often way off because time was still measured with a sandglass and speed was estimated by watching pieces of seaweed or wood pass by the hull.



Staff Navigation (Left) Early Speed Determination Device (Right)


Another useful navigational instrument of the time, around 1500 B.C., was the sounding reed or sounding weight. This device was used to figure out water depths in coastal regions. Using a combination of depth soundings, the sun or stars and the wind rose, these early navigators had to guess where they were when land could not be seen. The development of better navigational tools was naturally motivated by commerce and trade. The Phoenicians were most likely the first of the Mediterranean navigators to sail from coast to coast and even at night. The earliest known systems to aid the navigator were bonfires set up on mountaintops or large rocks.



Sounding Weight (left) Early Compass (right)


The first successful exploratory ocean voyages were probably achieved by navigational mistakes. Some of the reasons being: the ship was blown off course by a storm or influenced by a strong current or an error through a calculation made by the navigator, the best example being Christopher Colombo. Close examinations of his journals reveal that he did not know how to calculate latitude properly, so some of his determinations were far too high. When he discovered the Americas he actually thought he had reached India which explains why the names West Indies and Indians are still around to this very day.



Navigational instruments like the ones below were highly priced possessions in the early days of navigation.



Gallery Access


Additional info about historical navigational instruments:

http://www.seattleartmuseum.org/exhibit/interactives/spain/launchWin.htm



Italian Compass 1570 - The inner bowl with the compass face is mounted in a brass gimbal ring to reduce the effects of the ship's motion at sea. The soft iron needle is diamond-shaped and is fixed to the underside of the vellum and paper card. The compass face is divided into thirty-two points. Decorations on the north and east points were quite common up to the 19th century, wherby east for Europeans has been the direction of the Holy Land. Most early compasses were set in wooden bowls or boxes.  


The Sextant - The Sextant, not unlike some other navigational instruments, takes its name from its shape - the sixth part of a circle. Sextants for use in astronomy had been around since the 16th century but the marine version was developed around 1756/57 by Captain John Campbell, with the help of a London instrument maker named John Bird. The difference between a sextant and an octant is the lenght of its scale - up to 120 degrees but both work after the same principle.  


Persian Astrolabe 1660 - The astrolabe represents a mathematical likeness of the heavens and its Greek name is - "Star Taker". This amazing sophisticated scientific instrument has been crafted by Muhammad Mahdi al-Khadim al-Yazdi in brass and was used to solve astronomical problems and to show the positions of stars and planets at different dates, times and latitudes. The Persian calligraphy engraving reads a quotation from the Koran: "The world is decorated with stars".


Cross Staff circa 1700 - This particular Cross-Staff has been crafted by Thomas Tuttell, London, circa 1700.
The cross-staff was another instrument designed to measure the altitude of the sun or polar star. It made use of the properties of right-angled triangles, or trigonometry. The navigator or captain rested the main staff just below his eye and moved the cross until the bottom was aligned with the horizon level, and the top with the lower edge of star or sun. The position could then be read off on the scale in degrees and minutes. Cross-staves were mostly made of wood, but there are indications that some have been crafted in metall (brass) as well. Constantly looking at the sun with an instrument of this kind has often caused blindness.
 


Octant 1760 - The octant, also known as Hadley's quadrant, forms an eighth of a circle but the use of reflection doubles the angle, so that the scale reads up to 90 degrees. It has a radius of 17.75 inches (45.1 cm). Sir Isaac Newton developed the principle of the octant but is was not until 1731 when John Hadley demonstrated its use for marine purposes to the Royal Society in London. The use of mirrors to bring a reflected image of stars or the sun alongside the horizon, when viewed through the sight improved the accuracy of navigation considerably. This particular octant has been crafted by Benjamin Martin, London, circa 1760.


 


Spanish/Portuguese Astrolabe 1588 - The mariner's astrolabe has been developed by Arabic astronomers. Christopho Columbo used a similar astrolab design on his voyages to discover the "New World". It was a simplified version of an instrument for measuring the height of stars and the sun above the horizon level. This astrolabe has been discovered in southern Ireland were several ships of the Spanish Armada foundered.  


Mariner's Quadrant 1720/25 - The mariner's quadrant was one of the earliest devices developed for measuring angles, either of a star above the horizon level or the top of a hill in surveying. The name suggests, it consists of a quarter of a circle, with the curved edge divided into 90 degrees, a cord with an attached weight suspended from the point of the right-angle. The object was aligned through the sights on one edge, and the angle of elevation read off where the cord crossed the scale. This instrument is made of brass and its degree scale is subdivided for measurements to 30 minutes of arc.  


Gigantic Astronomical Sextant - Astronomical sextants had been in use since the 16th century.  


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