This is one of my sextants. It is a 1917 Kelvin & Hughes.   

The marine sextant measures the angle between two points. It is best known as an instrument for measuring the altitude of  the sun, moon, planets, or stars above the horizon. For centuries, it has been used as the primary tool to reliably navigate across open expanses of the world's oceans.

 The marine sextant is an equally useful tool for coastal navigation in the hands of a navigator adept in its use. With the sextant, the navigator can determine the range (distance) from an object of a known height, like a lighthouse or radio tower. The sextant can be used to establish a fix (location) by turning the sextant horizontal and measure the angle between two fixed objects. The sextant can be used to obtain an accurate time of day to set the ship's clock.

The voyage from New York City to Bermuda is planned to take five-and-a-half days. Although Distant Horizon has a primary GPS and 5 other devices that contain GPS receivers, two consecutive days will be dedicated to celestial navigation. The first two days of the voyage will use GPS. This is because the Automatic Identification System (AIS) receiver requires a GPS input. AIS provides important information from ships. It will take roughly two days to get far away from the shipping channels leading to NY. So, Safety first!