Sunday, May 13, 2012

How Did Early Navigators Use Celestial Navigation

One of the earliest devices used when men took to the oceans and seas to help them circumnavigate the planet was a mechanism called the Cross Staff. This type of device had many different uses, navigation, astronomy and surveying among them. A Cross Staff consisted of a main beam that was marked with graduations for length and a cross beam, also called a transom, that was used to gauge the altitude of the Sun, Moon or other celestial object from the horizon. With the angle converted to a value a relative location could be concluded. These devices were highly inaccurate tools for navigational purposes since they were susceptible to providing false readings on choppy seas.
Another early method of celestial navigation came directly from the Cross Staff and was called a Back Staff. The difference being that instead of gauging the angle or altitude of celestial object like the Sun or the Moon through the sighting of a Cross Staff, the Back Staff allowed the navigator to determine the angle more proficiently, efficiently and effectively through the projected shadows the sun or moon cast across the vertical or upper arm onto the horizontal or lower arm. These devices successfully replaced the Cross Staff and gave birth to newer navigational devices, such as quadrants, astrolabes and sextants.
The Mariner's Astrolabe was another early navigational tool that saw significant use by earlier seafarers. These devices incorporated the utilization of an inclinometer, which is also referred to as a tilt meter, tilt indicator or pitch & roll indicator. Strong evidence suggests and supports the notion that these devices were derived from the early planispheric astrolabe and were made out of brass since it was a heavier material and considered more suitable for conditions on the rough high seas. These devices were primarily used during the 17th century and were later replaced by easier to use navigational tools like quadrants and sextants.
The Reflecting Quadrant or Octant was another early invention that successfully replaced the Mariner's Astrolabe. These devices had many advantages over previous equipment and significantly reduced the instance for error when used properly, in comparison to early instruments like staffs and quadrants. There were several different versions created by a few inventors as far back as the early 1730's and by 1780 the octant and sextant had virtually replaced all older equipment used for navigational purposes.
The Navigational Sextant was also an early astronomical inception that was utilized to determine the altitude of a celestial object relative to the visible horizon in order to reasonably conclude a specific point on a nautical map locating a ships position. Most ships Captains still carry sextants on board as back up navigational tools in situations where the ship has experienced electrical power failure or has issues with its navigational equipment. All of these devices have one thing in common; they were used by ocean crossing seafarers to calculate positions on the sea by using the relative altitude of a celestial body and the horizon. Several improvements have been made in the field of navigational technology and these older devise are seldom used; however having the knowledge to properly use one of these devices may come in handy during an emergency situation while out at sea.
If you're new to the wonderful world of astronomy, or star gazing, a great outset would be Asynx Planetarium Software.
To download the software and to start your observations today, visit an invaluable source of information for beginners.
Christian Nuesch
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