Since the use of the ship's positioning system by GPSa saying has emerged that astronomical science has ended its eraand that the Sextant should be hidden inside museums.

To respond to this statement, we summarize the following:


Celestial Navigation is not limited to determining the position of the ship but it goes beyond that limited mission to the following important topics

  • Compass error setting
  • Definition of different time measurement systems and the relationship between them.
  • Knowledge of the foundations of the system of rising and setting celestial bodies.
  • Knowledge of the foundations of the annual movement of the sun and its effect on the phenomenon of night and day
  • Transforming the legal foundations of the times of the call to prayer for the five daily prayers into applied equations
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According to the International Maritime Organization IMO Celestial Navigation is still recognized as a method for determining the observed position of a shipand determining the ship's position by GPS is a confirmatory system.


The flight of many navigators from the application of Celestial Navigation in determining the location of the ship is attributed to several reasons:

  • Unfamiliarity with adjusting the marine sextant.
  • Unskilled in using the marine sextant to monitor the altitude of celestial bodies.
  • Awe of the length of the calculations to reach the elements of the position line
  • Unfamiliarity with determining the most likely observed location after drawing three or more position lines

To solve this dilemmamany available computer programs only require the navigator to observe stars or planets and enter data to obtain the most likely observed positionthus, the solution can be summarized in that the navigators are trained to control and use the marine sextant.

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It is worth noting that one of the most important duties of the navigator is to calculate the time of occurrence of any natural phenomenon for a sailing shipTherefore, the navigator resorts to applying the method of successive approximation This method consists of applying the following steps:

  • Calculate the future time of occurrence of the phenomenon using the ship's current position
  • Finding the ship's position at the time that was found in the previous step
  • Using the ship's last position to calculate the time of the future occurrence of the phenomenon again

Of course, the mathematical position of the ship can be obtained using the sailing map, or analytically using the following equations

d. Lat. = dist. Cos T.Co.

dep. = dist. Sin T.Co.

d. Long. = dep. / Cos (mean Lat.)

Natural phenomena that require finding their future time of occurrence while sailing

  • Morning civil twilight time to prepare for star observations
  • Sunrise time to check the compass error (amplitude method).
  • The accurate time of the meridional passage of the sun to find the Observed Latitude of the ship at noon
  • Sunset time to check the compass error (amplitude method).
  • Evening civil twilight time to prepare for star observations.


Dr.Adel Mostafa

It should be noted that these programs are available to my sons and fellow naval officers as a science to benefit fromThis is what was agreed upon by the work team, Eng. Islam Badawy, who designed these programsand my dear son, Ahmed Adel, who designed the required graphics.