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

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)

S E W N 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 – 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)

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 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!

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 ILDL

2. Fix everything wrt one place, e.g. Mecca

3. 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)