Published: Jan 30 2019
When you are out at sea in these modern days, you have your GPS and radar, along with carefully mapped charts and the sum of thousands of years of knowledge. For the majority of human history — until about 200 years ago — sailors navigated by the heavens alone. As the years went by, sailors developed more precise ways to calculate their position as they made the transatlantic crossing and traveled across all the world’s oceans.
The collection of methods that sailors used to find their way across seas that seemed to stretch into infinity is called celestial navigation and it is still quite accurate. Modern technology is easier to learn, but celestial navigation can guide you across the seas if you are able to master it.
This is not an easy thing to master, but it can be both fun and impressive. In the drastic case of broken or washed-overboard equipment, it could be quite useful. This is its main advantage: it needs nothing electronic, so you can do it regardless of battery life or the presence of electricity. The real disadvantage is that you cannot use methods of celestial navigation when the skies are cloudy, as you need to be able to see the stars or sun in order to use it.
Below is an introduction to celestial navigation, so you can begin to understand what it is all about. Keep in mind, however, that this tutorial is only a basic guide, and those wishing to learn the process to the fullest should look at the various tutorials, classes, and books available on the subject.
Celestial navigation pinpoints location through two key pieces of information. The first is the position of the star or heavenly body on which the observer is focused. The second is the angle between the horizon and the star. Think of it like a triangle. One point is the star and one point is the observer, with the third point being where the lines of the star’s height and the horizon meet.
In order to find these pieces of information, you need some special equipment and some time on your hands. Be aware: this method involves fairly complex mathematics, which are not explained here — just the general steps.
Here is what you will need:
Step one: Celestial navigation has to be done at precise times, especially if you are going to be using a star for your calculations. There are fifty-seven navigational stars in the navigational almanac, in addition to the sun and the moon. If you are going to be shooting a star (as finding its position is called), you need to do so at the precise time of day when the horizon line and the stars are both visible. You can find the position of the star with a starfinding website or program, of which several are available.
Step two: Once you have found the position of the heavenly body you are going to use for your calculations, use your sextant to measure the angle between yourself and the heavenly body. Make sure to note the exact time (in Greenwich Mean Time — GMT) at which you shoot it, and take this time down.
Step three: After this is done, you have to correct your measurements for variables such as the height above the horizon line. You will need a tutorial for this — search for “Henning Umland’s” and you will find a guide. After you make the corrections, you will have the observed altitude of the heavenly body.
Step four: Now go to the Nautical Almanac. This source will have data for the star or another celestial navigation point, and it will have the calculated altitude of the body against the locations. If your own calculation is off, you need to adjust your position by the number of miles which it is different.
Step five: Enter in the information for sight reduction (the term for information derived to establish a line of position). This includes the local hour angle, the assumed latitude, and the heavenly body’s declination. All of this information can be found either from your own calculations or in the Nautical Almanac. Once you have this, you will have the body’s height.
Step six: Plot your lines or position using a guide such as this: http://www.efalk.org/Navigation/plot1.html. Two lines will give you your exact position.
These lines form a broad-strokes picture of celestial navigation, which should give you a basic overview of how it works. To learn more, take a look at the section below.
This guide is only an overview of the basics. If you truly want to become expert in the art of celestial navigation, you should consider one of several options.
Online Courses — there are several courses that you can take online.
Books — if you prefer to study on your own, a number of books have been written on the subject of celestial navigation that go into the subject in great depth.
Classes — there are also a number of experts offering in-person classes. Look for one offered in your area.
It takes time and effort to master, but celestial navigation is truly one of the wonders that human civilization and progress have produced. As a mariner, you are part of this chain of history, and so with celestial navigation you can discover what it means to be where we are today.