An Introduction to Islamic Astronomy (al-Falak al-Shar’i)
Usama HasanIslamic Circles, Muslim World League,Saturday 25th Sha’ban 1428 /8th September 2007
With the Name of Allah, All-Merciful, Most Merciful
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 …
Synopsis
1. Geometry and Motion of the Earth
2. Qiblah
3. Prayer Times
4. Moonsighting
1 – The Geometry of the Earth
Latitude Longitude North Pole South Pole The Seasons
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
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)
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
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
1d – The Seasons: Earth’s Annual Motion around the Sun
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)
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
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)
Annual Motion of the Sun, Moon, Planets & Stars (Q. 55:17)
SE WN N
SUMMER SOLSTICE
WINTER SOLSTICE
EQUINOXES
Easts(Multiple, Two limits)
Wests(Multiple, Two limits)
Sunrise and Sunset
Season Sunrise direction
Sunset direction
Autumn East West
Winter SE SW
Spring East West
Summer NE NW
2- Qiblah formulae !!!
For Istanbul:
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
Examples of Great Circles
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.
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 ?
Tips for finding the qiblah - 1
Use The Plough and Polaris to determine North
In Somalia, Polaris tells us the qiblah!
Tips for finding the qiblah - 2
Use the direction of sunrise and sunset during the seasons
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
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
Tips for finding the qiblah – 4aLocal 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)
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
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.”
Daily Prayer Times (Solar)
Zuhr (Afternoon)
Asr (Late afternoon)
Maghrib (Sunset)
Isha (Night)Tahajjud (Late 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)
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?
Zuhr (Afternoon)
Immediately after Zawal (Noon)
Half-way between sunrise and sunset
‘Asr (late afternoon)
When sun is lower, cooler, yellower
One- or two- shadows’ length?
Easiest way to determine: half-way between noon and sunset
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 !
‘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?
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 …
4 - Moonsighting
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)
Phases of the Moon
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
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
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
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
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
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
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)
Calculating Crescent Visibility (2) Moonsighting.com is based on Yallop/Ilyas and
uses five factors only:
1. The angle between Sun and Moon2. The (angular) height of the Moon above the
horizon3. Earth-Moon distance4. Earth-Sun distance5. A measure of pollution in the atmosphere
Moonsighting.com’s predictions have proved accurate every month since 1994!
Crescent Visibility Curve – Tues 11 Sept 2007
Crescent Visibility Curve – Wed 12 Sept 2007 (eve of Ramadan 1428)
Crescent Visibility Curve – Thurs 13 Sept 2007
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 ILDL2. Fix everything wrt one place, e.g. Mecca3. Compromise: the Unified Hejra Calendar
(divide the world into three time zones)
Proposal 1: Crescent-Visibility curve as ILDL (International Lunar Date-Line)
1 Dhul Qa’dah 1426
30 Shawwal 1426
Proposal 2: Fix everything wrt one place, e.g. Makkah
Makkah
1 Dhul Qa’dah 1426
30 Shawwal 1426
Proposal 3: the Unified Hejra Calendar (www.icoproject.org)
Central Region
Western Region Eastern Region
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
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)