Praying five times a day is obligatory for Muslims at prescribed times that are related to the Sun's movement. Here comes the role of astronomy in determining prayer times using mathematics-based astronomical calculations.
The Dhuhr (the noon) prayer time commences when the Sun has passed its zenith; i.e. reaching the highest point in the sky, or passes the meridian. The zenith time refers to the midpoint between sunrise and sunset, and the meridian is an imaginary line that divides the sky into two parts, east and west, at which the Sun is at its maximum height, and the shadows are the least possible to completely disappear at the zenith point—the point that lies directly above the observer's head.
The Dhuhr time ends and the Asr (the afternoon) prayer time commences when the shadow of an object is equal to its height. The Asr time ends when the Sun sets and disappears below the horizon; that is, the time for Maghrib (sunset) prayer commences, and it ends by the disappearance of the twilight—the red glow of sunset from the sky. This, in turn, means the commencement of the Isha'a (evening) prayer time, which extends until midnight—in the middle of the period between sunset and sunrise. The time for Fajr (dawn) prayer commences at the true dawn, and ends at sunrise.
A false dawn is a pale white light that appears in the East, in the form of a triangle that points upwards, with the horizon at its base. It appears before the true dawn with a period ranging from half-an-hour to an hour. On the other hand, the true dawn is parallel to the horizon.
Prayer times are calculated by complex mathematical equations that involve several variables; including: longitude and latitude, local time, the equation of time (the difference between the standard clock and the sundial), and the inclination of the Sun. The calculations of the Fajr, Sunrise, Maghrib, and Isha'a prayer times share one equation, but the Asr prayer time has several equations.
The calculations of the Dhuhr, Asr, and Maghrib prayer times depend on the position of the Sun, which can be easily estimated scientifically. Estimating the prayer time of the Fajr and Isha'a depends on knowing the amount of sunlight, which cannot be predicted accurately in all cases due to several variables; including: geographical location, height above mean sea level, presence of natural obstacles as mountains and hills, and the different seasons of the year. With regards to the areas higher than the sea level, for example, we notice that the sunrise time precedes the areas at sea level, and the sunset time at the sea level precedes the heights; for this reason, the calculation of prayer times sometimes needs special equations.
In order to investigate the time of the Fajr and Isha'a prayers, the following must be taken into consideration: determining the phenomenon to be monitored, carefully observing from a dark place far from city lights, avoiding the use of any kind of lighting, and avoiding moonlit nights. In ancient and modern times, the time of dawn was noticed to commence when the center of the Sun is 18° below the horizon. Meanwhile, the Muslim World League and several Muslim countries adopt 18°, while Egypt adopts 19.5° and Morocco adopts 19°.
References
icoproject.org
Calislamic.com
Astronomycenter.net
Alperen.cepmuvakkit
Praytimes.org