Astronomical calculation for prayer time based on Islamic Law specification

In order to avoid the confusion caused by multiple computational methods, each prayer time is described in two ways: the astronomical phenomenon specified in Islamic Law  and the corresponding astronomical calculation. The latter is expressed in terms of the position of the sun above or below the horizon. Islamic scholars of prayer times determined the following:

  1. Fajr or Subh corresponds to the first appearance of a white light that spreads laterally across the horizon. This is referred to as true dawn and corresponds to when the sun is 18 degrees below the eastern horizon.
  2. Sunrise corresponds to the appearance of the highest point of the sun’s disk on the eastern horizon, which corresponds to when the sun is 5/6 of a degree below the horizon.
  3. Duhr corresponds to the sun passing its zenith – the highest point it will reach that day. This corresponds to the shortest shadow of an object [for that day].
  4. Ashr corresponds to the position of the sun such that the length of the shadow of an object is equal to the length of the object plus the length of the object’s hadow when the sun is at its zenith or the length of the shadow of an object is equal to the twice length of the object plus the length of the object’s shadow when the sun is at its zenith. The corresponding angle changes with respect to time and place. An alternative time for Ashr, considering Ashr prayer as Wustha prayer, is the middle between Dhuhr and Mashrib. This one especially will be applied when the time difference between Dhuhr and Ashr is less then 60 minutes, such that Friday prayer will be difficult to perform.
  5. Maghrib corresponds to the complete disappearance of the sun’s disk below the western horizon. This corresponds to the sun being 5/6 of a degree below the horizon.
  6. Isha corresponds to the disappearance of red twilight. This corresponds to the sun being 18 degrees below the western horizon.

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