If you love the sea and navigation, you’ve probably wondered how sailors could find their way across the ocean before GPS existed. The answer lies in instruments like the sextant, one of the most precise and fascinating navigation tools ever created.
Today, even though GPS and modern technologies have changed the way we explore, knowing how to use a sextant remains a valuable skill for any sailor who wants to keep an authentic connection with traditional seamanship.
What is a sextant and how does it work?
A sextant is an optical instrument designed to measure the angle between a celestial body (such as the Sun or a star) and the horizon. That measurement allows you to calculate your geographic position with remarkable accuracy—an essential skill before the advent of satellite navigation.
In practice, a sextant lets you determine your latitude and, with additional observations and calculations, your longitude as well, simply by observing the sky and the horizon. It’s a process rooted in the history of navigation, yet one that can still be extremely useful today when learned properly.
How to use a sextant: a step-by-step guide
- Prepare your instrument
First, make sure the sextant is properly calibrated and working correctly. Check the eyepiece alignment and the position of the mirrors to ensure accurate readings. It also helps to have a precise timepiece and the nautical almanac (ephemerides) on hand, which provide the positions of celestial bodies for a given time. - Find the horizon
Look through the eyepiece and try to align the horizon with the fixed mirror. In open water this is relatively straightforward, but be careful near high land or in heavy seas, as waves can make the horizon harder to read. - Observe the celestial body
Move the sextant’s index arm so the image of the Sun, a star, or another celestial object is reflected in the movable mirror. Keep adjusting until the celestial body appears to sit exactly on the horizon seen through the instrument. - Read the angle
Once the image is perfectly aligned with the horizon, take the reading from the sextant’s graduated arc. The angle you obtain is the altitude of the celestial body above the horizon—an essential value for calculating your latitude. - Calculate your position
Using the measured angle and the exact time, you can consult the ephemerides to determine your geographic position. With two or more observations at different times, you can refine the result and obtain an even more accurate fix on the chart.
Why learning to use a sextant still matters
GPS has certainly made navigation easier, but the sextant remains one of the most reliable tools because it doesn’t depend on electronics. Learning to use it gives you the ability to navigate without relying on technology—an important advantage in case of malfunctions or emergency situations.
Beyond practicality, there’s something truly fascinating and rewarding about connecting with the tradition of navigation, using the same type of instrument once used by the great explorers.
Your sextant: an investment in your passion
If you’re convinced that learning to use a sextant is a meaningful step toward improving your navigation skills, know that there are many options for every experience level. From simpler models—perfect for beginners—to high-quality sextants designed for experienced navigators who want maximum precision.
If you’re ready to take your navigation to the next level, explore our selection of sextants . Whether you’re starting your journey into the art of celestial navigation or looking for a reliable instrument for your next adventures at sea, you’ll find the right sextant for your needs.
