#HO MANY HOURS UNTIL SUNSET PLUS#
The dominant opinion in the Hanafi school says that Asr begins when the length of any object's shadow is twice the length of the object plus the length of that object's shadow at noon. The majority of schools (including Shafi'i, Maliki, Ja'fari, and Hanbali) say it is at the time when the length of any object's shadow equals the length of the object itself plus the length of that object's shadow at noon.
#HO MANY HOURS UNTIL SUNSET HOW TO#
There are two main opinions on how to calculate Asr time. * Isha angle is not explicitly defined in Tehran method.įor example, according to Muslim World League convention, Fajr = Dhuhr - T(18) and Isha = Dhuhr + T(17). Shia Ithna Ashari, Leva Research Institute, Qum Institute of Geophysics, University of Tehran The following table shows several conventions currently in use in various countries (more information is available at this page). There are differing opinions on what angle to be used for calculating Fajr and Isha. If the observer's location is higher than the surrounding terrain, we can consider this elevation into consideration by increasing the above constant 0.833 by 0.0347 × sqrt(h), where h is the observer's height in meters. We also obtain the equation of time (EqT) and the declination of the Sun (D) for a given date using the algorithm mentioned in the previous section.ĭhuhr can be calculated easily using the following formula: To calculate the prayer times for a given location, we need to know the latitude (L) and the longitude (Lng) of the location, along with the local Time Zone for that location. RA = arctan2(cos(e)* sin(L), cos(L))/ 15 ĭ = arcsin(sin(e)* sin(L)) // declination of the Sun
Naval Observatory computes the Sun's angular coordinates to an accuracy of about 1 arcminute within two centuries of 2000.ĭ = jd - 2451545.0 // jd is the given Julian date The above two astronomical measures can be obtained accurately from The Star Almanac, or can be calculated approximately. The sundial can be ahead (fast) by as much as 16 min 33 s (around November 3) or fall behind by as much as 14 min 6 s (around February 12), as shown in the following graph: It results from an apparent irregular movement of the Sun caused by a combination of the obliquity of the Earth's rotation axis and the eccentricity of its orbit. The equation of time is the difference between time as read from a sundial and a clock. These two measures are the equation of time and the declination of the Sun. There are two astronomical measures that are essential for computing prayer times. The next section provides information on how to calculate the above times mathematically for any location if the coordinates of the location are known.
The mean time from sunset to sunrise (or from sunset to Fajr, in some schools of thought). The time at which darkness falls and there is no scattered light in the sky. The time at which the Sun disappears below the horizon. The time when the length of any object's shadow reaches a factor (usually 1 or 2) of the length of the object itself plus the length of that object's shadow at noon.
When the Sun begins to decline after reaching its highest point in the sky.
The time at which the first part of the Sun appears above the horizon. These times are defined in the following table: To determine the exact time period for each prayer (and also for fasting), we need to determine nine points of time per a day.