Celestial navigation is a traditional form of navigation that was extensively used and highly reliable before the modern age of GPS technology. Is there any reason to learn this set of skills today? And if so, what are the best ways to learn it?
How Celestial Navigation Works
What is celestial navigation, exactly?
Let’s start with a modern perspective. GPS technology relies on satellites to determine your current position; you can navigate easier once that position is known. Celestial navigation also relies on external indicators to help you figure out your current position. The difference is that you’ll use the position of celestial bodies like the sun, moon, stars, and planets to do it.
One of the most important pieces of equipment you’ll use in celestial navigation is a sextant, which is a handheld device you can use to measure the precise distance between any two objects based on your current line of sight. With it, you’ll be able to determine how far a celestial body is from the horizon, as well as the distance between other celestial bodies.
There are a few different methodologies you can employ to calculate where you are and where you’re going using celestial navigation. Nearly all of them require using a measurement tool like a sextant, a way to measure time like a marine chronometer, and existing knowledge about how celestial bodies move.
For example, you can calculate your position using the intercept method. In this method, you’ll calculate a line of position (LOP) for yourself, determining a range of positions on the planet that are possible, given your observations.
You might measure the current angle of the sun and determine a range of possibilities for your current position. Then, you can measure a different celestial body, like the moon, sometime later, and determine a second LOP, and therefore a second range of possible locations. The points where these two lines cross is your precise location.
It's also possible to calculate your position with the help of a nautical almanac. Nautical almanacs publish information on the exact position of celestial bodies, including the sun, the moon, planets, the First Point of Aries, and 57 selected stars, all relative to the First Point of Aries. If you know where these celestial bodies are located, relative to each other and different positions around the globe, and you have enough information to start with, you can potentially determine your current position with only one measurement.
While using a sextant is by far the most accurate way to determine angles between objects, it’s possible to estimate angles by using your own hand. If you stand with your arm stretched out and your hand horizontally aligned with the horizon, the width of your pinkie finger will be equivalent to approximately 1.5 degrees.
Easy Ways to Estimate Latitude and Longitude
If you don’t want to dive deep into the world of celestial navigation, there are some tools you can use to estimate your latitude and longitude quickly.
You can measure latitude by looking for Polaris, the north star (in the Northern Hemisphere). This celestial body is always within 1 degree of the celestial north pole; if you measure it to be 8 degrees from the horizon, you can assume you’re about 8 degrees north of the equator. With simple tables, you can measure your latitude much more precisely, often within a fraction of a mile.
Longitude measurements are more dependent on knowledge of accurate time, since the Earth is constantly rotating at a rate of 15 degrees per hour. Without a timepiece, you’ll need significant knowledge of astronomical movements and several measurements to calculate longitude.
Otherwise, you can note the exact local time when the sun is at its highest point in the sky; you can estimate this by using a long, straight object and noting when the shadow disappears. Then, you can subtract your local time reading from Greenwich Mean Time (GMT) to determine how far east or west of the prime meridian you are.
Beyond the Basics
In this article, we've talked about the basics of celestial navigation, how it works, and how you can use it to determine your position on the sea. However, we've only covered the absolute basics, and to learn celestial navigation in more depth, you'll need a lot of education and practical experience.
To get that, you can pursue learning celestial navigation on your own with the help of a nautical almanac, online articles, and other practical tools. If you know someone who has a thorough understanding of celestial navigation, you can also talk to them or shadow them.
Otherwise, your best course of action may be getting formally certified as a celestial navigator through an organization like US Sailing. Their program will teach you how to use a sextant, how to calculate time, how to use Polaris sight, how to take measurements and make corrections, how to create and use a Universal Plotting Sheet, and more.
Should You Learn Celestial Navigation?
So, should you spend the time and money necessary to learn more about celestial navigation?
There are several motivations that may be driving you:
- An emergency backup. If your GPS device fails, if your communication equipment isn't working, and if you don't have a secondary way to navigate, celestial navigation can be an emergency backup. You may be more capable of communicating your exact position or finding your way back to land.
- Secondary measurements. Celestial navigation can also help you confirm whether your other methods of positional measurement are working correctly. You can verify all the information you're receiving by simply observing your surroundings.
- A fun parlor trick. Many people find celestial navigation to be fascinating. If you take lots of people on your boat at night, showing them how to calculate the position of celestial bodies could be a fun parlor trick and a great conversation starter.
- Personal satisfaction. Some people want to learn celestial navigation simply for the personal satisfaction of learning it. If you're always looking for new ways to challenge yourself, or if you like the idea of obtaining this new knowledge, that may serve as ample motivation for you to continue your education in this area.
Celestial navigation isn't strictly necessary to enjoy boating, especially in our modern era of reliable GPS technology. However, if you're looking to expand your skills as a boat captain, or if you just like the idea of being able to navigate in an emergency, celestial navigation could be a good fit for you.
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