Ahmed Shama (ashama@ucla.edu)
Tue, 07 Dec 1999 15:53:47 -0800
Bismillah al-Rahman al-Rahim
al-Salamu `alaykum wa Rahmat Allahi wa Barakatuh
Please feel free to circulate this e-mail widely. Contrary to the previous
e-mail, this information is useful to any Muslim who is looking for the hilal,
whether or not they live in California. The following information was obtained
from the website:
http://www.columbia.edu/~mnd/hintscrescent1.html
INFORMATION ON CRESCENT MOON SIGHTINGS AND HINTS
1. On an evening previous to the Moon Sighting evening,
it is advisable to FIND A PLACE WITH A CLEAR WESTERN
HORIZON (i.e. without any buildings or trees obstructing
the place where the sun sets, on the western horizon).
2. SET YOUR WATCHES to the correct time given by a time
service (usually through calling a telephone number).
3. FAMILIARIZE YOURSELF WITH THE QUESTIONS ON THE REPORT
and keep a copy in a file, for each month, with the
local islamic center. Mail a copy to the Islamic
Societies of North America (ISNA) at Post Office Box 38
PLAINFIELD, Indiana, 46168, U.S.A.
4. It should be noted that the actual PLACE OF THE SETTING
SUN varies with the seasons. In the northern hemisphere,
the sun sets to the north of west during the summer with
the extreme north setting on the summer solstice (June 22).
The sun sets due west on the autumnal equinox (Sept 22).
The sun sets south of west during the winter with extreme
south setting on the winter solstice (Dec 22). The sun again
sets due west on the spring equinox (March 21). In the
southern hemishpere, the directions from west are changed.
During the southern summer (when it is winter in the
northern hemisphere) the sun sets south of west.
5. Observe and note down the approximate angle of inclination
of the PATH OF THE SUN while it is setting. This inclination
of the path of the setting sun from the vertical is nearly
equal to the latitude of the observing location.
6. TO SEEK THE CRESCENT MOON. In order to obtain an idea as to
approximately where to look, the following information on
LUNAR ORBIT is useful.
a. The PATH OF THE CRESCENT MOON while it is setting
will be nearly parallel to the path of the setting
Sun. The path of the Moon will be CLOSE to the path
of setting Sun, being at a maximum of about 5 degrees
(usually it is less than the +/- 5 deg) `above' or
`below' the path of the sun, when observed from the
surface of the earth. (See Figure A.)
b. The CRESCENT MOON will also be TRAILING the SUN by
about 5 to 20 degrees, for a particular observing
point. The earliest sightings in the world would
have the moon trailing the sun by the least angle.
The Trailing angle of the Moon from the Sun can be
estimated from the Orbital details and the location
of the observer.
c. The DURATION OF THE FIRST SIGHTINGS of very young
moons may begin as early as 10 minutes after the
sun has set (to allow the twilight to reduce in
spectral intensity) with the first sightings being
usually before 20 minutes after sunset and the
sighting could continue for about 40 to 90 or more
minutes after sunset. The sighting would finally be
`fading' when the crescent is a few degrees above
the horizon. The fading is due to atmospheric extinction
caused by absorption. In order to isolate the Crescent
from twilight glare it is helpful to have any hollow
tube and to search for the crescent while looking
through the tube. (See Figure B.)
d. The HORNS OF THE CRESCENT MOON (i.e. the ends of the
approximately less than semi-circular arc of the
Crescent) will always point in a direction approximately
opposite to the location of the sun, the sun already being
below the horizon. (See Figure C.)
e. A general rule for MEASURING ANGLES in the sky is as
follows: When our hand is stretched out in front of us
(hand facing the sky)
a. each finger @ arm's length covers 1.5 deg @ our eye
b. two fingers " 3.0 deg "
c. four fingers " 6.0 deg "
d. closed fist " 10.0 deg "
e. outstretched fingers " 20.0 deg ".
(See Figure D.)
****************************************************************************
`APPARANT SIGHTINGS', HONEST AND SINCERE `MISTAKES'
· Of course, the Crescent Moon has to set and not
appear to `rise' in the western horizon. A WISP OF
CLOUD, which happened to be lit by the sun which has
already set, could easily be mistaken for a crescent.
This apparant `crescent' of cloud would travel with the
prevailing winds and would not set in a path nearly
parallel to the path of the setting sun. It could `rise'
instead of set or may travel north-east or south-east
instead of setting in the west.
· REFLECTIONS from high-flying aeroplanes. These
reflections of the sun on aeroplanes would not
have the semi-circular arced shape of the crescent
and the probability of their path being close to a
lunar path is minute. The reflections could disappear
while still being high up on the horizon.
· MOMENTARY VISIBILITY of the crescent. It might appear
that the crescent was `visible' for a moment by a single
Shahid (witness). A crescent would always be visible for
at least 5 minutes (if unobstructed by clouds, etc.) and
hence should be again visible by the person first seeing
it, and should be able to be seen by others in a group,
when pointed out. All should examine the crescent
carefully and try to ascertain its path and the direction
of its horns. A note should be made of the time of sunset,
time when the crescent was first visible and again the time
when the crescent faded away near the horizon. The vertical
angular height, which is the altitude of the moon should
also be noted at these times. The vertical angular distance,
which is the altitude of any heavenly body, is measured from
the horizon.
****************************************************************************
FIGURES
*******
FIG.A: PATH OF THE MOON RELATIVE TO THE PATH OF THE SUN
*******************************************************
(THIS DIAGRAM IS FOR A TYPICAL PLACE IN THE NORTHERN HEMI-SPHERE,
IN THE SOUTHERN HEMI-SPHERE, THE PATH SLOPES DOWN AND LEFT.)
\ \
--) \ \ (--------- Max. angular separation
\ \ +/- 5 deg (moon-sun paths)
\ \ P
\ \ A
\ \ T
\ \ H
P \ \
A \ \
T \ (( CRESCENT (HILAL)
H \ (( MOON --------------------------------
\ \\ // ^
O \ == (if moon's path is |
F \ `above' sun's path) |
\ |
S \ | \ O
U \ | \ F A
N \ | \ L
\ | \ M T.
/\ \ O
// \ \ O D
(90 - LATITUDE) =~ ANGLE of \ \ N I
(= COLATITUDE) Inclination | \ \ F
// | \ \ F.
========================= \ ================================
WESTERN | \ HORIZON |
| \ |
| |
| \/ SUN v
| --(@@)-- --------------------------
| /\ SUN
| (has already set)
|
| |
-----)| |(-----
| AZIMUTH |
DIFFERENCE
BETWEEN THE
MOON & SUN
FIG.B: ALTITUDE OF MOON AT SUNSET
*********************************
)
)) CRESCENT
)) MOON
))
)
/
/
/
/
/
/\ Angle of Height of Moon, above Horizon
/ \ = Altitude of Moon
( ) ----------------------------------------- \/ SUN
| / HORIZON - HORIZONTAL --(@@)--
|/ /\ SUN
|----- (has just set)
|
|
/ \
/ \
______________________________________________________
//////////////////////////////////////////////////////
GROUND GROUND GROUND GROUND GROUND GROUND GROUND
Height (degrees) of first sighting:
Height (degrees) of last sighting (fading) or moonset:
The heights (altitudes) of the crescent are to be noted not
only when it is first sighted, but also when it fades while
it is going lower in the sky, since the crescent could sometimes
fade away - due to atmospheric opacity - even before it sets in
the western horizon.
FIG.C: ORIENTATION OF ENDS OF CRESCENT
**************************************
AND ITS CURVATURE
The orientation of the Crescent is reported with reference to an
imaginary clock on the western horizon:
IMAGINARY CLOCK ON WESTERN HORIZON
12 'O Clock
|
___
( )
9 'O Clock -- ( ) -- 3 'O Clock
(( )) ----- HILAL (Crescent),
=== Shown from 4 through 6
| to 8'O Clock position,
6 'O Clock Double-Lines
CRESCENT 1: CRESCENT 2: CRESCENT 3:
( )
( )
( ( ) )
( __ __ )
==
From: 7 'O Clock From: 4 'O Clock From: 2 'O Clock
To: 10 'O Clock To: 8 'O Clock To: 5 'O Clock
Note: The Crescent orientations could be anywhere from around
the 2 'O Clock position to the 10 'O Clock positions.
The actual extent (length) of the crescent would
usually be less than 180 degrees, i.e.
2-7 (this would be 150 deg),
3-9 (this would be 180 deg),
4-9:30 (this would be 165 deg),
5-9:30 (this would be 135 deg) etc.
FIG.D: MEASURING APPROXIMATE ANGLES IN THE SKY
**********************************************
a. each finger at arm's length would cover about 1.5 deg at our eye,
b. two fingers " 3.0 deg "
c. four fingers " 6.0 deg "
d. closed fist " 10.0 deg "
e. outstretched fingers " 20.0 deg ".
---)| |(--- 1.5 deg for each finger.
( ) |
| |
|-----------
|
|
|
/ \
/ \
______________________________________________________
Angle 3.0 deg 6.0 deg 20.0 deg to thumb
Distance --)| |(-- --)| |(-- --)| |(--
Fingers )) || |||| __\||/ (( Fingers
Palm )) || || || (( Palm
Wrist )) ---- ---- ---- (( Wrist
No.of Fingers: 2 fingers 4 fingers 4 outstretched fingers and
****************************************************************************
****************************************************************************
****************************************************************************
APPROXIMATIONS TO DIRECTION OF KA'BA (MAKKAH Saudi Arabia)
**********************************************************
In most places of the UNITED STATES of AMERICA, an APPROXIMATION
to the direction of KA'BA, to determine the DIRECTION OF SALAT
(PRAYERS), can be obtained by noting the direction of your SHADOW
near the time of SUNSET. The direction in which your shadow goes
is usually a little north of east DURING WINTER. This is the
direction in which salat can be performed, as an approximation.
This direction of the shadow changes during the different months
of the year but is a good approximation when there is no magnetic
compass to determine the exact direction. During summer, the
shadow goes south of east and hence we would have to turn further
north from the shadow, ie. further to the left of the evening shadow.
For locations in the West of America the direction is even further
North from the shadow, ie. even further to the left of the shadow.
****************************************************************************
Copyright Dr.M.N.Durrani, 1987 to 1997
Permission to copy for free distribution is granted to all,
please do give credit and reference. Thanks.
For further information, please feel free to contact:
Mail: Dr.Mohib.N.Durrani
Islamic Amateur Astronomers Association
(Research Division)
601 West 113 Street, Suite 11-K
Columbia University
NEW YORK, N.Y. 10025
United States of America
Email to: mnd@columbia.edu
***************************** End of Document ******************************
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