“Where are we?” Well, we are safe and dry probably, working at home or shopping for the holiday season. But, this question has a different urgency if the ship is approaching a rocky coast and the life of the ship and its crew depends on a fast and accurate answer by the navigator.
So, what does a navigator needs to find the position of the ship on the earth’s surface?
A navigational sextant is an instrument that measures the angle between a celestial object and the horizon. The angle, and the time of measurement, the position of the ship on a nautical or astronomical chart can be calculated. Primarily used for celestial navigation, the sextants allow measuring the celestial objects relative to the horizon. The sextant in independent of electrical supply or human intervention and hence, considered as an eminent practical back-up navigation tool for ships even today.
Now, there are two types of sextant and the choice between them is entirely personal. Traditional sextants have a half horizon mirror dividing the field view into two. One half of the mirror provides the view of the celestial object and the other half of the mirror provides the view of the horizon. Whole horizon sextants use a half silvered horizon mirror providing only a full view of the mirror.
The development of sextant is attributed simultaneously to John Hadley of England and Thomas Godfrey of Philadelphia in 1731. The fundamental concept is to use two mirrors to make a doubly reflecting instrument – still followed in modern sextants. At Collectibles Buy, we have a wide collection of sextant instruments and other ship collectibles for purchase online.