Celestial Navigation, or astronavigation, is the science of navigating using what we see in the sky above us. It is one of the oldest ways of navigation among the seas and has declined with the invention of the GPS, but is still a very important skill to have. In an event of a GPS malfunction, knowledge of celestial navigation can help guide someone back to land!

Celestial navigation uses angle measurements between a celestial body and the horizon to tell you your position on the earth, be it on land or at sea. The most commonly used celestial body is the sun, but the moon and Polaris can also be used. In addition, there are certain “navigational stars” who coordinate are known that we can use to tell our position on the earth.

The tool most commonly used for celestial navigation is the sextant which can measure the angle between any two objects. By measuring the angle between a few celestial bodies and the horizon, one can calculate their position on earth. A sextant is accurate to a three-mile radius, which was incredible in the early-mid 1900’s, but is a wide margin for the technology we have today.

The Naval Academy has recently reinstated their celestial navigation courses for midshipmen. Around a decade ago, the Navy decided that they did not want to teach their students calculate their position on earth by hand. The midshipmen would continue to learn how to use a sextant, but would input that data into a computer rather that computing their position through mathematical equations by hand. The computers used by the Navy have improved the accuracy to a 60 feet radius. With fears around the security of the GPS and “desire to return to the basics of naval training“, the Navy has begun to return to its roots.

If you have any other questions or want to learn more about celestial navigation, Professor Susan Stewart is who you should contact. She is a professor here at Vanderbilt and specializes in celestial navigation for the Navy!