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www.birka.st

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Calculation method

The coordinates of the typed-in location is obtained from Google Maps. Thereafter, prayer times are computed using a variant of the program "prayTime" by Hamid Zarrabi-Zadeh (see documentation), which is based on commonly known astronomical model for the sun's apparent motion around the earth. This model has been used by Muslim since the 9th century Hijri. The program has been modified to serve the present purpose. In particular, the method of estimating Fajr and Isha times at persistent twilight has been changed. The times are given in the user's local time zone.

Validation of the program

The computed times were compared with modern astronomical tables, and were found to give the same results within the limit of round-off (+/-1 minute). The results were also checked against various Islamic prayer time tables for different locations in Sweden, spanning the entire range from latitudes 54° to 68°.

• The program reproduces the times given by US Naval Observatory for sunrise and sunset, if adjusted with 0.833° grader (standard adjustment for refraction plus sun radius).
• Times given by Astronomisk kalender are reproduced using an adjustment of 0.567° (standard refraction only).
• The prayer times given by the Islamic Academy are reproduced with an accuracy of 1 minute using 0.833° for Shuruq and Maghrib, and 18° for Fajr and Isha.
• The prayer times obtained from IslamicFinder are reproduced with 1-2 minutes accuracy using 0.833° for Shuruq and Maghrib, and selectable angle for Fajr and Isha, and applying "angle based" (this method is obtained in Birka using hilat=9, however it is not recommended, see discussion below).
• The prayer time tables published by IKUS for Scandinavia are reproduced with an accuracy of 1-4 minutes by using 1.73° for Shuruq and Maghrib, 20° for Fajr and 18° for Isha, plus a fix number of minutes added for safety to the different prayer times.
  
• The prayer times published by Islamiska Förbundet are reproduced for the winter months using 0.833° for Shuruq and Maghrib, 14.7° for Fajr and 13.7° for Isha. For the summer months the times for Fajr and Isha are constructed by interpolation algorithms that are not included in this program (for a detailed discussion of IFS's tables see here).
  

Sensitivity to location

The prayer time calculation is coupled with Google Maps, in order to get the coordinates for the typed-in location. The retrieved location is displayed in the address field, and also shown on a small map. It is also possible to type in coordinates on the format (latitude, longitude), and Google Maps will then find and display the nearest location. The map can be enlarged down to neighborhood level. E.g. typing in "Bjorns Tradgard", then zooming in a couple of times, one will find oneself in front of Stockholm's central mosque.

This facility of accurate location is needed, as will be seen from the below examples, comparing some cities in middle Sweden at about 200 km distance. The times in the tables are for July, 1, 2009:

Location	Latitude	Longitude	Shuruq (sunrise)	Zhuhr (noon)	Maghrib (sunset)
Stockholm	59.3°	18.1°	3:34	12:57	22:09
Örebro	59.3°	15.2°	3:46	13:08	22:20
time difference			12min	11min	11min

Stockholm and Örebro are on the same latitude, and the difference in longitude is 2.9°. This means the days are of equal length in the two locations, but the times are shifted by 11 minutes. As a general rule, each longitudinal unit gives a time shift of 4 minutes.

Location	Latitude	Longitude	Shuruq (sunrise)	Zhuhr (noon)	Maghrib (sunset)
Uppsala	59.9°	17.6°	3:29	12:58	22:17
Södertälje	59.2°	17.6°	3:37	12:58	22:09
time difference			+8min	0min	-8min

Times displayed

The following times are displayed:

• Fajr: The time when the center if the solar disk is a given number of degrees below the horizon. The number of degrees can be varied. The standard in Birka is 18°.
  
  
• Shuruq and Maghrib (sunrise and sunset): The times when an observer on earth first sees the upper edge of the sun appear, or sees it completely disappear below the horizon. These times are obtained by adding to the astronomically computed times
  
• (a) a compensation of the passage of the radius of the solar disk (0.27°)
• (b) a compensation f(Lat) for refraction. Birka uses as a standard an empirically based function f(Lat) that varies with latitude (see the section on Compensation for refraction).
• (c) a compensation H for the observer's elevation above sea level (this has not yet been implemented due to ongoing discussions on the subject).
  
  
• Zhuhr/Zawal: Noon (Zhuhr) time when the sun reaches its highest point during the day. The prayer time begins at Zawal, which is the time when the entire sun disk has passed an imaginary line suspended from the sun's highest point. The passage over this line is accounted corresponds to an angle of 0.54°, which is accounted for by adding 5 minutes to the computed noon time.
  
  
• Asr: The time when the shadow of an object is once or twice as large as the length of the object itself, plus the shadow it had at noon.
  
  
• Isha: The time when the center of the sun disk has moved a given number of degrees below the horizon. The number of degrees can be varied. The standard in Birka is 15° for al-shafaq al-ahmar and 18° for al-shafaq al-abyad.

Times that do not exist according these definitions are marked with "---". As a standard, the time of midnight (halfway from sunset to sunrise) is given in the Fajr column, when the Fajr-time does not exist. Estimated times are shown within brackets.

Other schemes can be computed by selecting "Special".


Settings

The following parameters can be varied:

• Address: name of location or coordinates (Latitude, Longitude)
  
• Elevation above sea level - not implemented
• Asr: 1 or 2 times the shadow
• Angles corresponding to [ dawn, sunrise, sunset, night ]
  If angles for sunrise and sunset are set to the value -1, the program will compute f(Lat).
• Hilat: interpolation scheme for Isha and Fajr at persistent twilight:
  0=None, 1=Midnight (only for Fajr), 2-8=1/2, ...., 1/8 of the night, 9="angle based" (more info here). If hilat is given a negative value, its absolute value will be used as an alternative angle for Isha when its normal time does not exist (applied when there is ikhtilaf about the time)
  
• Extra minutes for [ Fajr, Shuruq, Zhuhr, Asr, Maghrib, Isha ]

Note that in the program, night is taken as time from sunset to sunrise. (see more in the section Implementation of Taqdir).

Taqdir does not override existing times, except for Isha in the Hanbali madhhab, and when hilat=9 ("angle based"). All times that are the result of taqdir are marked by putting them between brackets.

These parameters are preset for the given options under "Compute times" according to the below table. They can be modified by selecting the option "Special".

Preset models

Metod	Asr	Vinklar	Addminutes	Hilat
Birka-Hanafi1	2	[18,   f(Lat), f(Lat),18/15]	[0, 0, 0, 5, 0, 0]	1
Birka- Shafi`i-Maliki1	1	[18,   f(Lat), f(Lat), 18  ]	[0, 0, 0, 5, 0, 0]	2
Birka-Hanbali1	1	[18,   f(Lat), f(Lat), 18  ]	[0, 0, 0, 5, 0, 0]	-90
Masjid2	2	[18,   f(Lat), f(Lat), 15  ]	[-10,0,10,0, 8, 0]	-80
Al-Ghazali- Hanafi3	2	[18,   f(Lat), f(Lat), 18  ]	[0, 0, 5, 5, 7, 0]	-15
Al-Ghazali- Shafi`i-Maliki3	1	[18,   f(Lat), f(Lat), 18  ]	[0, 0, 5, 5, 7, 0]	2
Istanbul4	1	[20,   1.73,   1.73,   18  ]	[0,-2, 5, 5, 7, 0]	1
Cairo5	2	[19.5, 0.833,  0.833,  17.5]	[0,-5, 5, 5, 5, 0]	1
Karachi6	2	[18,   0.833,  0.833,  18  ]	[0,-5, 5, 5, 5, 0]	1
Makka Umm al-Qura7	1	[18,   0.833,  0.833,   0  ]	[0,-5, 5, 5, 5,90]	1
MWL 20038	1	[18,   0.833,  0.833,  17  ]	[0,-5,0, 0, 5, 0]	3
MWL/ICOP 20098	1	[18,   0.833,  0.833,  18  ]	[-2,-2,2, 2, 2, 2]	3
ISNA true9	1	[18,   0.833,  0.833,  18  ]	[0, 0, 1, 0, 1, 0]	1
ISNA/IF10	1	[15,   0.833,  0.833,  15  ]	[0, 0, 1, 0, 1, 0]	9
MWL/IF11	1	[18,   0.833,  0.833,  17  ]	[0, 0, 1, 0, 1, 0]	9
Blackburn12	1	[14.7, f(Lat), f(Lat), 13.7]	[0, 0, 1, 0, 1, 0]	1

1. "Birka"(revised 2010-02-16): There are thre variants, covering the various madhhabs. According to Shafii, Maliki and Hanbali madhhab, Isha begins the passing of the red twilight. According to Observations and Fatawa, this is when the sun is about 15° under the horizon. For caution, however, the angle 18° is used. In the Hanafi madhhab there is ikhtilaf omn the Isha time (see Note). Therefore, both twilight angles (15° och 18°) are given for Isha  Hanafi also give two Asr  times (one and two times the shadow respectively). During periods off persistent twlight, Fajr is given as midnight. Isha is given for Shafi`i/Maliki at midnatt, for Hanbali 90 minutes after Mahgrib, and for Hanafi no time is given.
   
2. "Masjid" (introduced 2009-10-20): This option is intended for use in Masjids. It reflects the most lenient position regarding the Hanafi mahhab, giving for Asr: to times the shadow, for Isha: 15°, and in periods of persisten twilight 80 minutes after Maghrib. Safety margins are added to Fajr,Zhuhr and Maghrib.
3. "Alghazali-Shafi`i/Maliki" (introduced 2009-09-20): Because of the uncertainty in determining the end of the red twlight, the Al-Ghazali Institute recommends to use 18° for Isha. It is recommendet to pray Maghrib at its earliest time, and to delay Isha the end of the white twilight. (cf Note for the Hanafi madhhab). When the sun does not reach below 18°, midnight is used as taqdir for Isha, simulating "aqrab al-bilad"
   "Alghazali-Hanafi" (introduced 2009-09-20): Normally Isha is here taken as the end of the white twilight (18°). When this does not exist, the end of the red twilight is computed (hilat=-15 then gives 15° for Isha). When this also ceases to exist, no value is given.. A few extra minutes are added to Asr and Maghrib for cautiousness.
4. "Istanbul" simulates the IKUS time tables for Scandinavia.
   
5. "Cairo": According Dar al-Ifta al-Misriyya [reference missing].
6. "Karachi": According to University of Karachi [reference missing] (see also tables from the Islamic Academy).
7. "Makka": According to Umm al-Qura University [reference missing].
8. "MWL":  According to MWL fatwa 2003 nd 2009 respectively (Muslim World Leage/Rabita) [for Ref see Fiqh section].
9. "ISNA":  ISNA's critera are 18° for Fajr and Isha [for Ref see Fiqh section].
10. "ISNA/IF": Simulating IslamicFinder's ISNA option using 15° and "angle based" taqdir of Isha and Fajr. This method is not recommended - see - see Criticism of some current time tables. It is only included for reference.
11. "MWL/IF": Simulating IslamicFinder's MWL option using "angle based" taqdir of Isha and Fajr. This method is not recommended - see Criticism.
12. "Blackburn": simulating the Blackburn observation results. This option is not recommended - see Observations.
    
    

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