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Celestial Navigation

Celestial Navigation is a practice through which a navigating officer can plot the vessel’s position by observing the celestial objects i.e. the Sun, the Moon, and the Stars at any point on the planet. Nautical Almanac works as an essential tool in doing celestial navigation calculations and to get the location i.e. latitude and longitude or the Geographic Position (GP) of the particular celestial body. The angle between the celestial body and the visible horizon is directly linked with the distance between the celestial body’s GP and the observer’s position. After some sight calculations, these measurements are used to plot a line of position (LOP) on a navigational chart, the observer’s position lies somewhere on the line. Observation from two celestial bodies gives two such lines on the chart, intersecting and providing the observer’s position. To minimize the chance of error more than two celestial bodies can be used to get a more accurate position.

Celestial Navigation

What is Celestial Navigation used for ?

Celestial navigation is the ancient scientific art of position fixing that assists a navigating officer in transiting through the sea without relying upon estimated or dead reckoning calculations. Celestial navigation uses angular measurements taken between the celestial bodies and the visible horizon. The most commonly used celestial body is the sun, but navigators also use various other celestial bodies such as the Moon, the Stars, and especially the Polaris. For practicing Celestial Navigation at sea, the most basic equipment used onboard is the sextant, chronometer, chart of the particular region, Nautical Almanac, and sight reduction tables.

Celestial Navigation

What is the principle of Celestial Navigation ?

Celestial navigation is a method of discovering Geographic Position (GP) by observing celestial bodies. These Celestial bodies are projected on the celestial sphere, which is an imaginary sphere of infinite radius with earth being at the center. Celestial bodies are depicted as seen by an observer on the earth, all celestial bodies rise in the east, cross the observer’s meridian, and are set in the west, and have a common platform from east-west angles linked with the longitude and similarly common platform for north-south angle similar to latitude. The position of all celestial bodies that are used for Celestial Navigation can be tabulated for every hour of the day in two pages of the Nautical Almanac. Since all the calculations are based on angular measurements the radius of the celestial sphere is irrelevant.

What are 3 types of Navigation ?


In this era of the 21st century, with technologies and AI covering almost all types of industries, the mode of navigation in practice and high demand is the E-Navigation in which all forms of navigational operations depends on electric power and are much more efficient and accurate than any other type of navigation.


It is an ancient practice of navigating vessels out at sea using celestial bodies. It has global coverage, and this type of navigation can never be jammed. In the circumstances of blackout at open sea, celestial navigation is the only ideal solution to proceed.


This method of navigation is not possible in the open waters because any kind of landmark is required to practice terrestrial navigation such as the lighthouse, buildings, buoys, or any other possible object on the land. Bearings are taken from the landmarks to obtain the position, and it also assists in verifying the accuracy of electrical navigation.

How accurate is Celestial Navigation ?

The conceptual accuracy of position fixing through celestial navigation is under the range of 0.1 miles of your true position, getting a good amount of accuracy depends on minimizing every other source of error. Accuracy of a minute on the sextant can affect position fix accuracy by 1 mile.

Various sources of error can occur while practicing Celestial Navigation-

  • Errors identifying a celestial body
  • Calculation Error
  • Errors plotting the final position
  • Errors reading the measurement of sextant
  • Inaccuracies in chronometer
  • Errors in identifying prevailing atmospheric conditions

Hence, proper execution and practice can be used to reduce or eliminate most of the errors. An experienced navigating officer can faithfully expect an accuracy of around 1 mile while fixing position through celestial navigation. 

Do people still use Celestial Navigation ?

Celestial Navigation is becoming progressively unessential with the invention of an inexpensive and highly accurate satellite Global Positioning System (GPS). Nevertheless, a navigating officer shall never restrict oneself to just one means of navigation. If in any condition or circumstances every possible navigating equipment fails to w0rk, celestial navigation is the backup to proceed to a desired or safer destination. Hence, many National Maritime Authorities still require every navigating officer to show knowledge of celestial navigation.

Celestial Navigation as a primary tool for navigation is still used by private yachtsmen and long-distance cruising yachts. Onboard large merchant vessels out at open sea celestial navigation is practiced for examining the compass error.

How many stars are used in Celestial Navigation ?

Stars are luminous bodies that emit light and heat, under ideal conditions on a clear night around about 6,000 stars are visible by the naked eye. Out of these 58 stars are known to be used in the operation of celestial navigation. These stars are listed within the daily pages of a Nautical Almanac. Within the Almanac tabulated data is provided which is required for celestial navigation calculations. This data includes the Sidereal Hour Angle (SHA) and Declination (DEC) of each navigational star. While searching for the stars in the sky, a star map or a chart is required to make it easier to locate that particular star. Computer software is provided on the bridge to generate a localized star chart based on the vessel’s current location.

Celestial Navigation
Celestial Navigation


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