Navigators note in view of their constant wanderingsVariation in prayer times from one port to anotherEspecially if the latitude differs by a large amount and Muslims generally notice the difference in prayer times in the same location throughout the year The truth of the matter is that the timing of prayer depends on each of the following:

- The apparent position of the sun where the time of the year affects the distance of the sun from the celestial equator which is the coordinate which is known as the declination of the sun
- The geographical position of the observer on the surface of the earth especially the distance from the equator the coordinate which is known as the observer's latitude

To clarify the difference in the times of prayers at the same site in the following table we show the prayer times in the port of Alexandria (Arab Republic of Egypt) during the days of the spring equinox (March 21); summer solstice (22 June); Autumnal Equinox (September 23) and Winter Solstice (December 22).

To clarify the difference in the times of prayers at various positions of increasing north latitude; in the following table we show the prayer times for the equinoxes and solstices in three ports of increasing latitude:

- Port Sudan (19° 36`.0 N; 37° 15`.0 E)
- Istanboul (41° 04`.0 N; 28° 57`.0 E)
- Stockholm (59° 20`.0 N; 18° 03`.0 E)

We note that there is no prayer time for El-Fajr and El-Isha in the port of Stockholm on June 22 the explanation for this is that the legal condition for these two times is not met. We also note the great variation in prayer times with the change in latitude; Where:

- Prayer times are steadily increasing; with increasing latitude; on June 22nd, since the declination of the sun and the latitude of the observer are both north of the equator.
- Prayer times increase inversely with increasing latitude; on December 22nd, because the observer's latitude is north and the sun's declination is south.

There are many programs for determining prayer times for Muslims in specific locations and even the level of small cities in all countries of the worldbut for ships navigating the high seas whose positions are constantly changing the navigator resorts to calculating prayer times as well as the direction of El-Qiblahusing spherical trigonometry and adopting the method of successive calculation The author noted, by discussing with the brothers the navigating officers that the method of calculating for some of them differs greatly from the legal definition of the timings of El-Fagr prayer, El-Asr prayer, as well as El-Esha prayer

Hence, with the assistance of Eng. Eslam Badawy; a program was designed to calculate the times of the five daily prayers, as well as the direction of El-Qiblah for cruising ships according to the legal definition of the timings of each prayer and based on what is published in the annual book of the Egyptian Survey Authority regarding prayer times in the Arab Republic of Egypt

The legal definition of prayer times is related to the apparent positions of the sun on the surface of the celestial sphere It is obvious that the sun apparently revolves around the earth

(As a reversal of the Earth's rotation on its axis) a complete revolution in a changing time period called the Apparent Solar Day Hence, calculating the prayer time for a particular site we first calculate the apparent position of the sun according to the legal definition Expressed by the value of Local Hour Angle then we calculate the corresponding apparent solar time and finally convert it to the mean solar time

The following is the legal definition of prayer times corresponding to the apparent position of the sun at the beginning of the time according to what was stated in the annual book of the Egyptian Survey Authority And special prayer times in the Arab Republic of Egypt

The mathematical basis to determining the direction of El-Qiblah from any location on the surface of the earth is the Principles of sailing calculations on the Great Circle.

So if we assume that the position of Makkah Al-Mukarramah is M and the position of the observer is N The direction of Makkah Al-Mukarramah from position N is the initial course (supposedly) for the path of the great circle from site N to site M

The current program is designed to find the true direction of El-Qiblah on this mathematical basis where the location of Makkah Al-Mukarramah is (21º 25`.3 N; 39º 49`.5 E)

Apply it nowIt is applied to any celestial body that has a low altitude (less than 15°) and in exceptional circumstances up to (35°) in order to avoid reflects the direction of the object on the mirror of Azimuth Mirror device. For higher altitudes, the compass error is not recommended The following figure shows the solution sequence in the time method on the basis of which the program was designed..

Apply it nowThe second method is used during theoretical sunrise or sunset it is clear that this method is limited time and restricted body for use This method is called the amplitude method It should be noted that in order to observe the direction of the sun during the theoretical sunrise or sunset we must first know what the theoretical sunrise or sunset is Theoretical sunrise or sunset occurs when the true altitude of the center of the sun's disk is zero It occurs when the altitude of the lower limb of the Sun's disk is approximately equal to its angular radius That is, to monitor the direction of the sun in this case the position of the sun disk must be as shown in the following figure:.

Therefore, great care must be taken when using this method at higher latitudes this is evident from the following figure.

At high latitudes the sun rises or sets at a small angle of inclination with the circle of the horizon and then the compass bearing of the sun may differ by a significant amount (0.5° → 1°.5) if it is not in the correct position and then the compass error is inaccurate

The following figure shows the solution sequence in the Amplitude method on the basis of which the program was designed.

Apply it nowOne of the primary tasks of the Navigator is to prepare for star sights during morning twilight or evening twilight The calculation is made on the basis that the middle of the period of observing the stars is the beginning of the civil twilight in the morning or the end of it in the evening

This is evident from Figure (1) for the sequence of sunrise phenomena and Figure (2) for the sequence of sunset phenomena

The program was designed on this basis.

The importance of preparing for observing stars lies in the fact that the observer is often unable to recognize the name of the star to be observed because the stars may not be visible in their constellations in the morning due to the accumulation of clouds, for example, or the incomplete appearance of these groups in the evening.

The current program gives a map of the observer's horizon at the time of civil twilight indicating on it the navigational stars that are likely to be observed and also showing the ship's course in order to clarify the relative direction of each star relative to the sides of the ship.

Also given is a list of the names of those stars and the altitude and bearing of each of them After that, the navigator chooses the stars that he will observe according to the following priorities

- To be distributed over the entire horizon circle.
- To be at close altitudes (as far as possible)
- To be of close magnitudes (as much as possible).

In many shipping companies the navigator must report the ship's position at noon This requires the implementation of several steps:

- Determining the Greenwich Mean Time GMT (to the nearest second) at the moment of the sun's transit over the meridian of the observer (the ship) in advance.
- Observing the sextant meridian altitude of the sun at that moment.
- Extracting the declination of the sun (Dec.) (from the nautical almanac tables; at that moment
- Correcting the sun's meridian altitude to get the true meridian zenith distance (T.M.Z.D.).
- Apply the following equation to get the observed latitude of the ship

True Lat. = T.M.Z.D. + / ~ Dec

Determining the Greenwich Mean Time (to the nearest second) at the moment of the sun's transit over the observer's meridian in advance is the problem because the sun moves on its daily apparent diurnal circle and the ship moves on its course at the same time Therefore, the navigator resorts to calculating the Accurate Greenwich Mean Time at the moment the sun crosses its meridian by the method of successive approximation Which requires many steps of the solution and thus the increased possibilities of error The program for determining the Accurate Greenwich Mean Time of the ephemeral was designed with the assistance of Engineer Islam Badawy; to solve this problem.

Apply it now