An introduction-to-islamic-astronomy

1. An Introduction to Islamic Astronomy (al-Falak al-Shar’i)
Usama Hasan
Islamic Circles, Muslim World League,
Saturday 25th Sha’ban 1428 / 8th September 2007
With the Name of Allah, All-Merciful, Most Merciful

2. Who will benefit, in sha’ Allah
Students of Islamic law (Shari’ah)
Students of mathematics, physics, astronomy, etc.
Mosque imams
Mosque time-keepers (muwaqqits)
Others …

3. Synopsis
1.Geometry and Motion of the Earth
2.Qiblah
3.Prayer Times
4.Moonsighting

4. 1 – The Geometry of the Earth
Latitude
Longitude
North Pole
South Pole
The Seasons

5. Motion of the Earth
The Earth spins on its axis once in 24 hours (from west to east): one day and night
The axis of the Earth’s spin is inclined at 23.5 deg to the direction of its motion around the Sun

6. 1a - Latitude
The Equator
The Tropic of Cancer (23.5 deg N)
The Tropic of Capricorn (23.5 deg S)
Local latitude is given by the altitude of the North Star (northern hemisphere only)

7. 1b - Longitude
The Greenwich Meridien
Lines of longitude as time zones
360 deg / 24 = 15 deg
The International [Solar] Date Line (ISDL or IDL): 180 deg E / W

8. 1c – The Poles
At the North Pole, all directions are South
At the South Pole, all directions are North
The North Star (Pole Star, Polaris, al-najm al-shimali, najm al-qutb) is directly above the North Pole
The Earth’s axis points to the North Star

9. 1d – The Seasons: Earth’s Annual Motion around the Sun

11. The Seasons (cont’d)
At the Spring & Autumn equinoxes, the Sun is directly above the Equator
At the Winter Solstice, the Sun is directly above the Tropic of Capricorn
At the Summer Solstice, the Sun is directly above the Tropic of Cancer
(For northern hemisphere: vice-versa for the southern hemisphere)

12. The Seasons – Implications for Shadow Lengths
Between the Tropics (i.e. in Tropical and Equatorial regions of the earth), there are times during the year when the Sun is directly overhead at noon
Shadows sometimes disappear at noon
Outside the Tropics (north and south), the Sun is never directly overhead at noon
Shadows never disappear at noon

13. Annual Motion of the Sun, Moon, Planets & Stars
“Lord of the Two Easts, Lord of the Two Wests!
So which of the favours of your Lord will you deny?”
(al-Rahman 55:17-18)
“Lord of the East(s) and West(s) …”
(Muzzammil 73:9, Ma’arij 70:40)

14. Annual Motion of the Sun, Moon, Planets & Stars (Q. 55:17)
S
E
W
N
N
SUMMER SOLSTICE
WINTER SOLSTICE
EQUINOXES
Easts (Multiple, Two limits)
Wests (Multiple, Two limits)

15. Sunrise and Sunset
Season
Sunrise direction
Sunset direction
Autumn
East
West
Winter
SE
SW
Spring
East
West
Summer
NE
NW

16. 2- Qiblah formulae !!!
For Istanbul:

17. Qiblah Direction: Great Circles
A “Great Circle” is a circumference of the Earth that has the centre of the Earth at its centre
All lines of longitude are Great Circles
No line of latitude is a Great Circle, except for the Equator, which is a GC
There are many inclined Great Circles

18. Examples of Great Circles

19. Comparison of Great Circle Route and Loxodrome on the Mercator Projection. The loxodrome is a line of constant heading, and the great circle, although appearing longer than the loxodrome, is actually the shortest route between New York and London.

20. Qiblah direction
The correct qiblah direction is always a “Great Circle” direction
… unless you believe that the Earth is flat
E.g. from the USA, is the qiblah SE or NE ?

21. Tips for finding the qiblah - 1
Use The Plough and Polaris to determine North
In Somalia, Polaris tells us the qiblah!

22. Tips for finding the qiblah - 2
Use the direction of sunrise and sunset during the seasons

23. Tips for finding the qiblah - 3
At noon (zawal), the Sun is always:
Due South if you are north of the Tropic of Cancer
Due North if you are south of the Tropic of Capricorn
Between the Tropics, it will be overhead, N or S

24. Tips for finding the qiblah – 4 (Khalid Shaukat): When the Sun is overhead at the Ka’bah:
It is not advisable to determine the Qibla specially for a Masjid using an ordinary compass. The following method which uses the sun is more reliable and accurate. It has been observed for centuries and reported in many books by Muslims around the world that two times a year the sun comes overhead above Ka'bah. This is observational fact for centuries, and is used to set the correct Qibla direction in places far from Makkah by Muslims for last so many centuries.
Those two dates and times are:
May 28 at 12:18pm Local Civil Time at Makkah
July 16 at 12:27pm Local Civil Time at Makkah

25. Tips for finding the qiblah – 4a
Local Time facing sun gives Qibla
PLACE
May 28
July 16
Afghanistan
13:48
13:57
Bangladesh
15:18
15:27
Bosnia
11:18*
11:27*
Burma
15:18
15:27
Canada, Montreal
15:18*
5:27*
Egypt
11:18
11:27
France
11:18*
11:27*
Germany
11:18*
11:27*
India
14:48
14:57
Indonesia,Jakarta
16:18
16:27
Iran
13:48*
13:57*
Malaysia
17:18
17:27
Pakistan
14:18
14:27
Palestine
12:18*
12:27*
South Africa
11:18
11:27
United Kingdom
10:18*
10:27*
* means that these times are local Daylight Saving Times as observed in those countries.
This method applies at local Makkah noon between and around these two dates also, because Makkah is only two degrees from the Tropic of Cancer, i.e. the method applies throughout May, June and July with good accuracy (UH)

26. Tips for finding the qiblah - 5
Use a compass or qiblah compass
Magnetic north is near true north
Effect of metal / steel structures, e.g. inside modern office/apartment blocks

27. Tips for finding the qiblah - 6
If all else fails …
Most satellite dishes in UK point SE !
Hadith, “What is between the East and the West is the qiblah,” based on the ayah, “To Allah belongs the East and the West: wherever you turn, there is the Face of God.”

28. Daily Prayer Times (Solar)
Zuhr (Afternoon)
Asr (Late
afternoon)
Maghrib
(Sunset)
Tahajjud (Late Isha (Night)
night)
Fajr (Dawn)
Duha (Forenoon)
“Establish the Prayer from the Decline of the Sun until the Darkness of the Night,
and the Dawn Recitation …” (Qur’an, 17:78)

29. Fajr (Dawn)
False dawn, “like fox’s tail”
True dawn
Angle of Sun beneath horizon: 12-18 deg?
90-minute rule for the UK
Impossible to calculate precisely?

30. Zuhr (Afternoon)
Immediately after Zawal (Noon)
Half-way between sunrise and sunset

31. ‘Asr (late afternoon)
When sun is lower, cooler, yellower
One- or two- shadows’ length?
Easiest way to determine: half-way between noon and sunset

32. Maghrib (Sunset)
When the whole of the sun’s disc disappears below the horizon
Calculations of sunset (and sunrise) have an error of 1-2 minutes either way because of refraction
Important for prayer and iftar !

33. ‘Isha (Night)
When the red or white twilight disappears
When it gets dark & the stars come out
Angle of Sun beneath horizon: 12-18 deg?
90-minute rule for the UK
Impossible to calculate precisely?

34. Tips on Prayer Times
Try not to use a watch or prayer timetable!
But if you must …
Problem of Fajr / Isha time in the Summer …

35. 4 - Moonsighting

36. The Moon - Basic Facts
The Earth travels around the Sun once every 365 days (and 6 hours)
The Moon travels around the Earth once every 29 ½ days
A lunar year of 12 lunar months has 355 days
Phases of the moon result from parts of the Moon reflecting the Sun’s light towards the Earth
A lunar month has either 29 or 30 days (hadith)

37. Phases of the Moon

38. Looking for the New Crescent
Only visible after sunset
Must wait for the sun’s glare to die down
Experience shows that the best time to see the crescent is about 20 minutes after sunset (when the sun is 5° below horizon)
Perfect timing if the Sunnah is followed (Salat al-Maghrib should be fairly short)
Look at the western horizon, near where the sun set

39. The MOONWATCH Project
Launched 1st Oct 2005 & will run for several years (www.crescentmoonwatch.org)
A mass-experiment for the UK public
Part of Einstein Year (2005 is 100 years since the publication of Relativity theory)
Everyone is encouraged to look for the new crescent every month and report their observations via the above website
Will help improve HM Nautical Almanac Office’s crescent-visibility calculations, in sha’ Allah

40. Moonsighting - History
The Islamic calendar is a purely lunar one
Islam abolished the Pre-Islamic Arabian method of intercalation
Until relatively recently, the start of each lunar month was determined purely by observation of the new crescent moon
If cloudy, use a simple alternating 29/30 day rule
Communication constraints meant there was no controversy across the vast Muslim lands

41. Moonsighting – Islamic Law (1)
The Shari’ah (Sacred Law) covers all areas of life
Basic rule: crescent-sighting establishes the new month
Calculations: controversial; different views
Cannot be used to determine new month
Can be used to reject false crescent-sightings
Can be used to determine new month

42. Moonsighting – Islamic Law (2)
Applicability of a valid crescent- sighting: two views that can be unified
One view: ikhtilaf al-matali’ (“multiple horizons”)
Crescent-sighting applies only “locally”
Nowadays: each state has its own horizon
Another view: ittihad al-matali’ (“unified horizons”)
A single sighting applies for the whole (Muslim) world

43. Background - Calculations
Accurate calculations for the position of the moon have been around for thousands of years
E.g. solar and lunar eclipses
However, calculation of the visibility of the new crescent moon has only become significantly accurate over the last ~20 years
Yallop, Ilyas, etc.
Usually, the moon needs to be 15-25 hours old before the crescent is visible
Using conjunction (“astronomical birth”) means the month will start one day too early

44. Calculating Crescent Visibility
Simple prediction rules have existed for millenia (ancient Babylon, Greece, classical Islam, e.g. al-Bayruni, etc.)
Modern criteria have been developed by:
Bernard Yallop (ex-director of the Royal Observatory Greenwich)
Mohammad Ilyas (Malaysia)
Schaefer (kept the details secret)
Odeh (Jordanian Astronomical Society)

45. Calculating Crescent Visibility (2)
Moonsighting.com is based on Yallop/Ilyas and uses five factors only:
1.The angle between Sun and Moon
2.The (angular) height of the Moon above the horizon
3.Earth-Moon distance
4.Earth-Sun distance
5.A measure of pollution in the atmosphere
Moonsighting.com’s predictions have proved accurate every month since 1994!

46. Crescent Visibility Curve – Tues 11 Sept 2007

47. Crescent Visibility Curve – Wed 12 Sept 2007 (eve of Ramadan 1428)

48. Crescent Visibility Curve – Thurs 13 Sept 2007

49. Towards a Unified Lunar Calendar
With accurate calculations of crescent- visibility, a worldwide lunar calendar is now possible (Ahmad Shakir, Qaradawi, Kamali, etc.)
There are 3 major possibilities:
1.Use the visibility curve as an ILDL
2.Fix everything wrt one place, e.g. Mecca
3.Compromise: the Unified Hejra Calendar (divide the world into three time zones)

50. Proposal 1: Crescent-Visibility curve as ILDL (International Lunar Date-Line)
1 Dhul Qa’dah 1426
30 Shawwal 1426

51. Proposal 2: Fix everything wrt one place, e.g. Makkah
Makkah
1 Dhul Qa’dah 1426
30 Shawwal 1426

52. Proposal 3: the Unified Hejra Calendar (www.icoproject.org)
Central Region
Western Region
Eastern Region

53. Proposal 3: the Unified Hejra Calendar (www.icoproject.org)
Central Region
Western Region
Eastern Region
For Dhul Qa’dah 1426, ILDL coincides with the Solar dateline

54. Links
www.crescentmoonwatch.org
http://websurf.nao.rl.ac.uk
UK_Islamic_Astronomy yahoogroup
www.moonsighting.com
www.jas.org.jo (Jordanian Astronomical Society)
www.icoproject.org (Islamic Crescent Observation Project)