Modern marine electronics such as radar, GPS and chartplotters, have made it so much easier for yacht owners to drive their own vessels. But, if you do not have a Captain, and you are an owner operator, you should never be 100% reliant on such equipment. In the event of an emergency or system failure, could you navigate your yacht without your GPS or other electronics?

The Basics Of Celestial Navigation

“And all I ask is a tall ship and a star to steer her by…” is more than a line from John Masefield’s famous poem, Sea Fever. Seafarers have been navigating by the stars for centuries, and you can too!

Celestial navigation may be a bit more complicated than just plugging a waypoint into a navigation system, however, it can guide you just about anywhere on the high seas, if you study and care to master it. In times of dire emergency, when modern tech could be unavailable, being able to navigate by the stars like our seafaring ancestors, could prove a most valuable skill!

This is not an easy skill to master, and it requires some special equipment, and some complex mathematics. An article like this should be taken only as a brief introduction and overview.

The key to celestial navigation is “triangulation.” It requires a star or other heavenly body upon which you can focus, and measuring and tracking the angle of that star and the horizon using a device known as a sextant. In addition to the sextant you will need:

  • An accurate watch or clock. If you need to check its accuracy, you can compare it against the Navy’s master clock, found here. (
  • A current nautical almanac. Make sure that you buy an official almanac — the government puts out a very extensive version.


Marine Navigation Without Electronics

Here are the basic steps to celestial navigation. Again, complex mathematical computations are involved which have been left out of these steps.

Step one: Celestial navigation has to be done at precise times, and on a clear night, 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.

Step two: Once you select and identify your heavenly body, you use the 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.

Step four: Now go to the Nautical Almanac. This source will have data for the star or other celestial navigation point, and it will have the calculated altitude of the body against the locations.

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.

Chart of Northern Navigational Stars

Chart of Northern Navigational Stars


Chart of Southern Navigational Stars

Chart of Southern Navigational Stars

Step six: Plot your lines or position using a plotting sheet.  Two lines will give you your exact position.

This is just a very broad overview of how celestial navigation works. If you would really like to learn the skill, there are many online courses, or wonderful workbooks available.

A Typical Plot Sheet

A Typical Plot Sheet

Aids To Navigation for Motor Yachts

Even if you never want to be a modern day Christopher Columbus, and be able to navigate by the stars. Beyond knowing how to use you GPS, any boater should also be familiar with the basic Aids To Navigation, or ATONs. Unlike on the on the highway, you will not find any road signs or traffic signals out on the water. What you will find are various “ATONs.”

The U.S. ATON system is maintained by the U.S. Coast Guard. It consists of visual, audible, and electronic signals which are designed to assist boaters in the process of navigation. ATONs include: buoys, day beacons, lights, lightships, lighthouses, radio beacons, fog signals, marks and other devices used to provide “street” signs on the water. The aids to navigation system is not intended to identify every shoal or obstruction to navigation which exists in the navigable waters of the United States, but rather provides for reasonable marking of marine features as resources permit.

ATONS are “coded” with odd and even numbers, red and green colors, and other markings.

A complete guide to understanding symbols and colors of the various ATONs and what they mean, has also been published by the USCG.


On Demand Yachting Provides Peace of Mind

When it comes to making sure you and all of your guests are as safe as possible, understanding basic marine navigation and the “rules of the road” is only part of the equation. In the unlikely event it is ever needed, you must also ensure that you have all the right safety gear on board, and it is always ready and operational. That means PFDs need to be checked and replaced, fire extinguishers maintained and recharged as necessary, first aid kits restocked, etc.

Also, tantamount to avoiding accidents and other trouble at sea, is making sure your yacht is clean, detailed, and properly maintained. Maintaining your yacht’s safety gear, and ensuring that her engines and other critical systems are always at operational readiness is just one of the services you can count on from our On Demand Yachting Solution.



Operating a motor yacht can be costly. You can reduce your expenses, and avoid costly repairs by keeping her well maintained. On Demand yachting from FYM can help. If you would like to learn more, or if you have any questions or comments about this blog post, do not hesitate to contact our Yacht Management specialists, or call us at (954) 900-9968.