What Is Celestial Navigation and the Tools to Do It?

When Christopher Columbus voyaged across the Atlantic Ocean in 1492, he relied on the cosmos to guide his ship. Despite the rise of new technologies making exploration easier than ever, celestial navigation is far from an outdated method of finding one’s way. 

Using astronomical observations — such as the sun, moon, stars or planets — one can find their location on Earth and get where they need to go. Often used in maritime, this navigation type has saved many lives on the high seas, providing a backup to modern techniques and preserving a snippet of history.

A Brief History of Celestial Navigation

Oceanic navigation is over 4,000 years old, starting with the Phoenicians in 2000 BC. Historians also discovered a device called the Antikythera mechanism in 1900 near a shipwreck believed to belong to ancient Greeks. The flat bronze device — which had many gears and wheels —  may have been the world’s first analog computer during the 3rd and 2nd centuries BC.

Global navigation systems were entirely transformed by the 16th century as seafarers learned to determine latitude. They used angle-measuring devices like an astrolabe to discover the sun’s altitude at noon and the ship’s latitude. 

Eventually, the mariner’s compass and nautical charts became much more valuable for sailors to record their trips. Today, celestial navigation is a critical skill for those sailing beyond the visual scope of land, especially since modern technology is not always reliable. 

The Basics of Astronavigation

While celestial navigation is a practical method, there is much to learn. For starters, astronavigation begins with understanding the celestial sphere — an invisible sphere on which all celestial objects exist. While the sphere remains fixed, the Earth rotates in the opposite direction once daily, enabling a well-defined coordinate system. 

Like any discipline, there are several other key terms explorers should know when learning about this primitive navigation technique, including the following:

• Altitude: A celestial object’s angular distance over the horizon
• Azimuth: How the celestial body is positioned, clockwise from true North
• Greenwich hour angle: Angular western distance of the Greenwich celestial median through 360°
• Local hour angle: Angular western distance of the local celestial meridian facing westward through 360°
• First point of Aries: Where the sun crosses the equator from South to North, known as the Vernal Equinox
• Geographic position: The point on the Earth’s surface where the celestial body is directly overhead

There is other terminology a person must know when using astronomical observations to navigate the world, but these are essential terms.

Essential Tools for Celestial Navigation

Celestial navigation is not the most straightforward method for getting from one place to another. After all, explorers have 100 billion stars to choose from as celestial bodies in the Milky Way galaxy alone. Fortunately, several instruments and resources can help with the navigation process. 

• Sextant: A digital or traditional device used to measure a celestial body’s angle to the horizon, helping navigators determine latitude
• Chronometer: A precise clock for Greenwich Mean Time calculations to find the longitude at sea, taking the celestial bodies’ position into account
• Nautical Almanac: A yearly publication with critical information and observations about celestial objects
• Sight reduction tables: Pre-calculated altitude and azimuth values to help determine and chart a Line of Position (LOP)
• Navigation tables and calculators: Practical resources and tools to identify stars and ensure accuracy
• Magnetic compass: Helps navigators determine the direction they are going in
• Plotting tools: Allows for charting routes and positions

How to Take a Sight

To take a sight, a navigator must use a sextant to observe a celestial object and gather information. This requires them to alter the mirrors and ensure the device works properly to view the sun, a star or a planet. 

The noon sight is among the most critical measurements in astronavigation. In this method, an explorer determines the latitude according to the sun’s maximum height above the horizon at local noon, when the sun reaches its highest point in the sky. 

One must look at the sun through the sextant every 30 seconds, observing how the sun climbs higher than the original angle measurement. The sun will peak at local noon, at which point it will start to go down. The highest point before its descent is essential for finding the latitude.

Noon sights are not the only measurements required for accurate celestial navigation. A noon sight provides the latitude, but longitude is also necessary. Navigators must collect insights from several celestial sources at different times to identify their position correctly on a nautical chart. 

Determining the Line of Position

Mariners need two clues to find the LOP — a charted line where they might be situated. For instance, an explorer uses a sextant to see the sun or a star to determine where they should be if the celestial body is angled where they measured. They will then refer to the Nautical Almanac, various tools and statistical measurements to specify the time of day and where the celestial object is positioned. 

The intercept is the distance between the LOP and the assumed position. For this method to work, an individual needs two or three exact LOPs that intersect — the United States Navy requires two coordinates to make a calculation. However, it is crucial to note that inaccurate measurements and timekeeping could hinder accurate results.

Modern Celestial Navigation

It is not uncommon for people to overlook technological wonders as certain tools become ingrained in society. For instance, the Global Positioning System (GPS) was initially intended for military use but extended to civilians in 1983 following Russia’s takedown of a Korean Air Boeing 747. Today, GPS is integrated into new car models and mobile phones, while airlines and mariners utilize the technology for accurate navigation.

Yet, despite widespread GPS availability, celestial navigation remains vital as a reliable backup when digital systems fail. As an adventurer or sailor, knowing how to navigate terrain or high seas by following the stars provides greater safety, reconnects people to the past and passes along the unique skills of early explorers.

The Stars Will Light the Way

Modern devices are convenient and precise. However, the stars are just as helpful in guiding the way home. Although it might be more complicated than opening a smartphone app, adventurers on land or at sea should learn astronomical navigation as an alternative plan to avoid getting lost. If anything, becoming self-reliant and maintaining its historical significance should inspire all explorers to learn this valuable skill.