At sunrise, during the day or at dusk, when the division between sea and sky is a distinct horizon, the Captain and Mates of RV Revelle practice the traditional mariners’ art of celestial navigation.

Standing outside of the bridge, away from their electronic radar and Global Position System (GPS) they hold up the ship’s sextant, a tool that measures the angle of the Sun, Moon, planets or stars from the horizon. These celestial bodies help determine our ship’s position at sea and can check the accuracy of our compasses.

“If you look at three different stars and measure their distance from the horizon, there is only one place in the world where all the angles intersect,” says Eric Wakeman, the Chief Mate. “And that's right where you’re at.”

During the day, as the sun passes overhead, the Mates can also use the sextant to measure different angles of the sun above the horizon. If they also know the accurate time, these angles allow them to calculate their position.

“When we are not busy with dredging or other station operations, we take pride in being able to do celestial navigation and get an accurate fix,” says Captain Chris Curl.

Tonight, with blue whales feeding on krill and Fernandina swallowing much of the southwestern horizon we took a reading off of three stars: Arcturus, Spica and Dubhe, which is the last star on the ladle of the Big Dipper. Sure enough, the position we calculated from those sightings matched where 3 satellites in the GPS constellation have us plotted.

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