The Moon orbits Earth once every 29.53 days (average of synodic month). Because of this revolution, phases of the Moon change as the Moon's position change relative to the Earth and the Sun. So, during the Moon's orbit, if the Moon, Earth and the Sun lie exactly at the same line and the Moon in the middle, the Sun will illuminate half of the Moon that faces it, and the other half which faces us, will be dark because it does not reflect rays of the Sun (However, due to the inclination of the Moon that might reach up to 6 degrees, it may reflect a very small percentage of Sun's rays, but according to my information no observer yet reported seeing such crescent) . At this point, the Moon is called Wane or New Moon. After that, the Moon continues orbiting the Earth and begins to reflect a small amount of Sun's rays and now we see the Moon as a very small waxing crescent. Afterwards, it becomes first quarter, full Moon, last quarter, waning crescent and then wane again.
Moon's age is measured from the moment of the wane (New Moon). We often
say this Full Moon is 14 days old, which means that the number of days
since the wane is 14. And we say this crescent is about 2-3 days old. But,
did any one ask himself what is the minimum age of crescent that we can
see ? Generally, through a telescope, it is not likely to see a crescent that is less than 10
hours, i.e. if we want to observe the thin waxing crescent to determine the beginning
of an Arabic month, the Moon must be in the wane phase (New Moon) 10 hours ago or
more. But why?!
The wane Moon (New Moon) is located exactly at the Sun's direction, so the Sun's
glare will prevent us from seeing it, in addition, the percentage of the
reflected rays out of the wane Moon (New Moon) is equal to zero, and this percentage
increases as the Moon's age increases. Thus, GENERALLY human eye through
a telescope can't detect any reflected rays from the Moon if the Moon's
age is less than about 10 hours.
* When to Locate the Waxing Crescent?
The new waxing crescent is located near the Sun, so we shall wait until Sunset, because it is obviously impossible to observe the thin waxing crescent before Sunset. In addition, we must wait a reasonable time until the twilight decreases, i.e. until we can differentiate between Moon's light and twilight glare, a 10-minute period could be enough sometimes to detect the thin waxing crescent.
* Where to Locate the Waxing Crescent?
As mentioned above, the wane Moon (New Moon) is located exactly near the Sun. If we assume that the Moon will set when it is wane (New Moon), generally it will set along with the Sun, but we are looking for a crescent of 10 hours old, which means that it is still near the Sun. So, we must look at the west, a little bit over the Sunset point.
* When the Waxing Crescent Sets?
The Moon, like the Sun, rises from the East and sets after about 12 hours at the west (with exceptions at high-latitude areas), and since the waxing crescent lies near the Sun, it will set after the Sunset, and in its best cases, the new waxing crescent sets about one hour after the Sunset.
* Are the 10 hours only, enough as a factor to determine the crescent visibility?
Of course not. There are several factors that must be met in order to view the thin waxing crescent: one of these factors is the crescent's altitude, it must be about 3 degrees or more, and the angular distance between the centers of Sun and Moon must be 5 degrees or more (number of degrees from east to west equals to 180 degrees), and the Moon's staying ( the interval between the Sunset and the Moon set) must be 12 minutes or more. But we must realize that an excess of one of these factors may compensate the lack of another factor, i.e. if the angular distance between the Moon and the Sun is 10 degrees and the Moon's altitude is just two degrees, then the big angular distance may compensate the small Moon's altitude.
* What's the Meaning of Astronomical Calculations of the Crescent?
Most people think that the astronomical calculations mean absolute determination of crescent visibility, but this is not true, the astronomical calculations include the following:
* Conclusion:
To locate the thin waxing crescent, we have to start looking for it after a
while of the sunset at the West, a little bit above the point at which
the Sun sets, in its best cases, crescent sets about one hour after Sunset.
You will find below a table showing the crescents viewing conditions during
1998.
The New Moon phase is defined as the instant at which the apparent celestial longitudes of the Moon and the Sun are the same. Considering the Sun, Moon, and the Earth to be points not disks. Adopting this definition, the New Moon phase is certainly a unique instant all over the world. But in reality the Sun, the Moon, and the Earth are viewed as disks not points, and so, observers on the Earth in different locations will not see the centers of the Sun and the Moon at the same longitude in the same instant. The difference may reach up to four hours. This would be obvious during a solar eclipse, which can be considered as a "visible" New Moon phase, since it is well-known that a solar eclipse does not begin at the same instant all over the world.
For most purposes, it is suitable to consider the New Moon phase as a unique instant all over the world, and so, nearly all the astronomical books and magazines publish times of New Moon phase as a unique instant, which is for the center of the Earth. But to observe the very thin crescent
shortly after the New Moon phase, and to know the exact interval between the New Moon phase and the observation time (Moon's age), we should adopt the instant of the New Moon phase that occurs from the location of observation. Consequently, times of the New Moon phase in this document are calculated for Amman, or for Iraq in the Iraqi report.
To calculate the Topocentric new Moon, prayer times, and Qiblah direction, kindly download the program "SalatTimes" by Ali Alhadad.
Many thanks for those who assist JAS, their efforts are highly appreciated. Furthermore, JAS welcomes any other comments or suggestions.
Remarks Concerning The Table:-
The Space and Astronomy Group, in the Physics department, Baghdad
University in Iraq, sent us a report concerning the crescents of the religious
months that they saw from 1987 to the beginning of 1997. They hold
B.Sc. in Astronomy or Physics, and work at the Iraqi National Astronomical Observatory.
- Location of the Observatory (Place of Observations): Koreok Mountain,
Al-Mossul, Northern Iraq.
- Coordinates of the Observatory
- The Instruments:-
- Conditions in this place:-
* Remarks Concerning the Table:-
The following criteria for crescent visibility are adopted by Prof. Hamid M.K. Al-Naimy, an astronomy Professor at Al al-Bayt University (after two years of observing crescents), and by Mr. Awni Khasawneh, who holds a M.Sc. degree in astronomy from the same University (after studying many sightings of the crescent), and by JAS.
There is not a unique method adopted by all the Islamic countries to start the Islamic months. There are many methods spread all over the Islamic World, some of them are:-
Most people think that Saudi Arabia always adopt the actual sighting of
the crescent as the basis to start Islamic months. But during
the previous years, it was very clear to the public as well as to
astronomers that most of the Saudi months were wrong if the actual sighting
is the basis for starting the Islamic month. Fortunately, JAS received a telegram from The Highest Religious Council "Majlis al-Ifta' al-A'ala" in Saudi Arabia confirming that Saudi Arabia adopts the astronomical calculations and totally ignores the actual sighting. Below is a literal translation of this telegram.
"( To Jordan/ Al-Yadodeh/ M.Kh./ Al-Sook/ Mr.
Hayel Mamdooh Abu-Zeid, dated January 21, 1998/Ramadan 23, 1418H.
We wish to thank you for sending us your greetings of Ramadan, and for
reminding us of the date of the New Moon of Shawwal for the year 1418 H.
We would like to remind you that determining the first day of the Islamic
month is like determining the prayer times, and the aim of His Almighty
from these times is to inform us not to take it as worship. It is adopted
in Umm-ul-Qura Calendar that if the Moon's age at Sunset is 12 hours
or more after the New Moon then the PREVIOUS day is
the first day of the Islamic month, since the Islamic day starts at
Sunset, and the night is before the daylight, as well as the time of
fasting is in the civil daylight. May Allah accept your worship. May
Allah bless this Ramadan. Thanking you for your good cooperation.
From: Kingdom of Saudi Arabia/ Al-Riyadh/ The Higher Religious Council "Majlis al-Ifta'
al-A'ala"/ Mohammad Bin Ehmead.)"
Mr. Hayel of JAS received other letters also, about the same subject, which were clearer than this telegram. The
following example may make their system clearer: If for example 29th Dec
is 29 Sha'ban, and the New Moon Phase occurs after Sunset in Riyadh,
say at 11 pm on 29th Dec., then the next day (30th Dec.) at the Sunset
(For example at 5 pm) the Moon's age will be 18 hours which is more than
12 hours, so that day (30th Dec.) is the first day of Ramadan, even though
the New Moon was not even born at the Sunset on 29 Sha'ban (29th Dec.),
and generally in such cases the Moon will set before Sunset!! Below
is a copy of the telegram.
To calculate Moon's Phases kindly Download Moon
2.2.
" The program and text are interesting, and a spot check of one year's
lunar phases certainly appears to show that the results are quite accurate.",
Mr. Roger Sinnott, Associate Editor in Sky&Telescope Magazine.
"New MOONS" Not "New MOON" !!
Comments from Scientists Concerning the above Paragraph
However the geocentric configuration is a useful one for distant objects but of course the Moon is near.
Of course the centres of the Earth, Moon and the Sun are rarely in line - this corresponds to a total solar eclipse. At other times, locations away from the line, there is a crescent Moon. Thus even at New Moon from any particular location the crescent will change in extent and position. Likewise when New Moon is defined for a particular observer on the Earth, as the Moon and Sun sharing the same celestial longitude (Right Ascension), the crescent will be positioned either north or south near to but not necessarily centered on the poles of the Moon (libration of the Moon defines the extent to which it appears to wobble). Of course there will be a line roughly in longitude where all observers on the Earth will see the Moon and Sun at the SAME Right Ascension."
Visibility of Crescents from Amman, Jordan in 1998
Month NewM Time Sset Mset Mage Mstay Dis Alt Visibility Begin Name DD/MM hh:mm hh:mm hh:mm hh:mm mm d:mm d:mm Shawwal 28/01 06:52 17:11 17:35 10:19 24 4:40 02:54 Difficult 29/01 Thu Al-Kea'dah 26/02 20:43 17:36 17:26 -03:07 -10 02:05 -03:44 Impossible 28/02 Thu Al-Hejjah 28/03 04:21 17:58 18:27 13:37 29 07:16 04:09 Possible 29/03 Muharram 26/04 16:01 19:18 19:20 03:17 02 04:58 -01:17 Not Possible 28/04 Safar 25/05 23:16 19:38 19:14 -03:38 -24 06:00 -06:21 Impossible 27/05 Rabeea' Awwal 24/06 05:22 19:51 20:02 14:29 11 07:48 00:24 Difficult 25/06 Rabeea' Thani 23/07 18:03 19:45 19:35 01:42 -10 3:31 -03:37 Impossible 25/07 Jamadah Al-Aulah 22/08 03:34 19:18 19:35 15:44 17 06:17 01:39 Difficult 23/08 Jamadah Al-Aakherah 20/09 20:52 18:41 18:44 -02:11 03 01:53 -01:13 Impossible 22/09 Rajab 20/10 11:56 17:03 17:23 05:07 20 04:01 02:16 Difficult 21/10 Sha'ban 19/11 04:38 16:40 17:10 12:02 30 05:55 04:17 Possible 20/11 Ramadan 19/12 00:21 16:40 17:20 16:19 40 07:32 05:43 Possible 20/12
NMoon = Day of the New Moon.
Time = Time of the New Moon as seen from Amman.
Sset = Sunset on the New Moon's day.
Mset = Moon set on the New Moon's day.
Mage = Moon's age (The time in hours and minutes between the New Moon and the Sunset).
Mstay = Moon's staying (The time in minutes between Sunset and the Moon set).
Dis = The distance in degrees between the centers of the Moon and
Sun at the Sunset.
Alt = Altitude of the Moon's center in degrees at Sunset.
Visibility = The probability of seeing the waxing crescent through a telescope
on that day from Amman assuming a clean and high area.
Begin = The first day of the month. Which is the following day of the expected day of seeing
the waxing crescent.
Longitude: +35:52
Latitude: +31:58
Elevation: 975 mIraqi Observations for The Crescents
Unfortunately these instruments were crashed during the Iraq-Iran War,
and during the Second Gulf War ! So the following crescents were seen by small telescopes
such as 8 inches.
Day Date Month Year Alt Dis Age Mstay Friday 23/10/87 Rabeea' Awwal 1408 -00:12 10:59 20:19 12 Monday 16/05/88 Shawwal 1408 07:24 09:39 18:04 59 Thursday 14/07/88 Thu Al-Hejjah 1408 05:09 08:38 19:01 43 Thursday 06/04/89 Ramadan 1409 04:34 07:11 12:55 37 Friday 05/05/89 Shawwal 1409 00:55 04:44 02:48 19 Monday 03/07/89 Thu Al-Hejjah 1409 03:12 05:57 13:07 33 Tuesday 27/03/90 Ramadan 1410 08:50 11:16 18:59 59 Saturday 23/06/90 Thu Al-Hejjah 1410 07:12 11:49 21:06 56 Sunday 22/07/90 Muharram 1411 01:14 06:53 14:51 20 Monday 15/04/91 Shawwal 1411 10:33 11:14 19:23 62 Friday 12/07/91 Muharram 1412 03:49 12:08 21:02 34 Friday 03/04/92 Shawwal 1412 02:53 06:17 11:29 28 Monday 01/06/92 Thu Al-Hejjah 1412 02:59 06:05 13:44 32 Tuesday 23/03/93 Shawwal 1413 01:25 05:12 08:31 20 Sunday 20/06/93 Muharram 1414 01:02 07:30 15:50 19 Wednesday 18/08/93 Rabeea' Awwal 1414 -01:13 12:49 20:23 06
Saturday 12/03/94 Shawwal 1414 01:26 05:05 08:34 19 Tuesday 31/01/95 Ramadan 1415 06:33 08:57 16:03 48 Monday 19/02/96 Shawwal 1416 05:56 08:22 15:46 44 Thursday 18/04/96 Thu Al-Hejjah 1416 04:22 07:59 17:04 36 Thursday 09/01/97 Ramadan 1417 04:01 06:20 11:01 36
Our Criteria for Crescents Visibility
If the crescent satisfies these conditions, it is expected to be seen through telescopes from a highly-elevated and clear area. Knowing that an excess of one of these factors may compensate for the lack of another, for instance, if the angular distance between the Moon and the Sun is 10 degrees and the Moon's altitude is just two degrees, then the big angular distance may compensate for the small value of the Moon's altitude.
Looking at the West | Just Before Sunset |
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