Moon Sighting

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The moonset of the first Day of lunar month

Moon sighting (Arabic: رؤية الهلال) means sighting the crescent of the new moon and is one of the ways to prove the beginning of a lunar month in religion. A remarkable amount of obligatory and recommended acts of worship and rituals such as hajj, fasting, al-Qadr night and some legal issues such as increasing diya (blood-money) in haram months depend on the moon sighting at the beginning of the month. For determining the beginning of the month, Shi'a jurists have different criteria. Different astronomical conditions influence the sighting of the crescent as well.


A remarkable amount of obligatory acts of worship such as hajj and fasting, and many recommended rituals which are specific to a certain timing, as well as some legal issues such as increasing diya (blood-money) in the haram months depend on the moon sighting of the beginning of the month. Therefore, the ways of proving the beginning of a lunar month are discussed in the jurisprudential books. The importance of this issue is more in the month of Ramadan and becomes more sensitive especially in determining the end of this month so that if the month of Ramadan is twenty-nine days, the next day after the last day would be Eid al-Fitr when fasting would be forbidden, otherwise, it would the thirtieth of the month of Ramadan and fasting is obligatory.

This sensitivity and doubt existed in the past as well and hadiths are transmitted from Imams (a) which well show these conditions; however, in the more recent years, with the expansion of communications, sighting or not sighting the moon in different cities and even countries has increased this doubt and perplexity so much that even in one city, two different days have been announced as the Eid al-Fitr.

In verse 189 of Qur'an 2, moon sighting and its importance in religious rulings are mentioned, "They question you concerning the new moons. Say, 'They are timekeeping signs for the people and [for the sake of] hajj." In volume ten of Wasa'il al-Shi'a, the chapter of "Abwab ahkam shahr Ramadan" (issues regarding the rulings of the month of Ramadan), more than a hundred hadiths are mentioned about the details of sighting the crescent of the new moon.

In Islam, all things have spiritual dimensions as well and the crescent of the moon too is not an exception to it. In supplication 43 of al-Sahifa al-Sajjadiyya, Imam al-Sajjad (a) addresses the crescent of the moon and talks to it. There are also supplications for sighting the crescent of every month and the months of Rajab and Ramadan.

Ways of Determining the Beginning of the Month

According to Shi'a jurisprudence, the beginning of a lunar month can be determined in one of the ways below:

  • A person himself sees the crescent of the moon.
  • Gaining confidence in the report of others or other rationally acceptable sources.
  • Testimony of two just men whose report is not in contradiction to astronomical rules.
  • If thirty days have passed since the first of the previous month.
  • The verdict of the Shari'a ruler (according to the views of some religious authorities)

Astronomical Analysis

The beginning point for determining the age of the crescent is the moment of simultaneity of the moon and the sun (new moon).[1] Upon the simultaneity of the moon with the sun, the part of the moon which faces the earth is obscure and is not visible and "goes on the wane" in astronomical terminology. When the moon goes out of the wane (i.e. obscurity), it should be seen as a slender crescent, but the crescent is too narrow to be sighted. With the movement of the moon and going away from the sun, the moon becomes visible as a crescent.

The duration of time from when the moon moves until it becomes visible is called "taht al-shu'a'" (literally "under the beam"). Astronomically, the duration of obscurity plus "taht al-shu'a'" takes about forty hours and forty-eight minutes. On the other hand, turning the moon around the earth does not always fit on the circle of zodiac[2] and this variation influences the moon sighting. The possibility of sighting the moon and thus the announcement of the beginning of a lunar month in (geographically) western countries is more than in eastern countries.

Influential Criteria

The age of the crescent at every moment equals the time passed after the moment of simultaneity of the moon and the sun. It might firstly be thought that the more the age of the crescent is, the easier its sighting will be because with the increase of the age of the crescent, the moon has more time to go away from the sun, and its angular separation increases and thus the bright surface (phase) of the moon increases; however, there are different factors which influence the moon sighting, some of which are mentioned below:

Height of the Crescent

One of the common terminologies regarding the crescent is the height of the moon from the horizon. The height is the angle between the horizon and the object. The height of the moon is one of the criteria influential in the sighting of the moon. The less is the height of the crescent, its light passes through thicker layers of atmosphere and its brightness lessens and its sighting becomes more difficult.

Difference of Side

Among other criteria influential in moon sighting is the difference between the sides of the moon and the sun. It refers to the difference in angle between the moon and the sun at the time of the sunset.

Duration of Pause

Vespertine crescents set below the horizon after the sunset. The duration of time between the sunset and the moonset is called the "duration of pause". The more is the duration of the pause, the longer the moon will be in the sky, the sky becomes darker and the possibility of the sighting increases. Duration of the pause of narrower crescents is less than one hour and in some cases, less than 40 minutes. Usually, such crescents cannot be sighted after the sunset and the observer has to wait until the appropriate time comes.

Thickness of the Middle Section

One of the expressions used regarding the crescent is the thickness of its middle section. The more this thickness is, the more the possibility of moon sighting will be.

The thickness of the crescent in the second or third nights cannot be evidence for the wrong beginning of the month, because the orbit of the moon around the earth is oval, and depending on where the moon is on its orbit at the present time, it goes away from the sun and its bright part thickens.

Time of Sunset

Since vespertine crescents are seen after the sunset, the later the sun goes down the age and angular separation of the crescent increases. Therefore, the more we go toward western areas, the better the conditions of sighting the crescent will be.

Distance between the Moon and the Earth

Since the orbit of the moon around the earth is oval, according to Kepler's second law, the speed of the moon in turning around the earth is not fixed. It simultaneity happens when the moon is around below its orbit, it goes farther from the sun with a higher speed and its separation will be faster. Such a crescent is much easier to sight in comparison to a crescent of the same age at its peak.

Reasons for Difficulty of Sighting the New Moon

  1. Crescents of the beginning and the end of the month are usually slender.
  2. These crescents are usually near the sun [in sighting] and thus they are outshined by the sun's great light.
  3. The moon has a short distance from the horizon and the line of sight (or in other words, the light of the moon) passes through a thicker layer of the atmosphere; and thus, dust, humidity, and atmosphere disturbance makes sighting more difficult.
  4. Due to the closeness of the moon to the sun, the duration of the crescent's pause above the horizon is short and the observer has little time for the moon sighting.

Records of the Moon Sighting and their Usages

Records of the moon sighting are the lowest limits of the influential criteria of the youngest moon sighted. One of the basic methods of analyzing the possibility of sighting the crescent is by comparing the astronomical criteria of the crescent with the records. If the astronomical criteria influential in the moon sighting have better values than the records, it can be claimed that in case the appropriate conditions are provided, an experienced observer can sight the crescent.

In the evening of August 18, 2001, Alireza Movahhednejad managed to sight the crescent of the month of Jumada l-Thani, 1422 AH (August 2001) by a 40*150 binocular. The age of the moon at that time was 12 hours and 15 minutes and its angular separation from the sun was 7.6 degrees. This way, the record of the moon sighting was set for Iran. The next year, Mohsen Qazi Mirsa'id managed to sight the very young crescent of the month of Rajab, 1423 (September 2002) at the age of 11 hours and 40 minutes and set a new record by his name.

Difference of the Criteria between Different Countries

In different countries, there are different criteria for announcing the lunar month: some countries only consider the sighting of the moon valid, some rely on the astronomical calculations, some consider both the sighting of the moon and the astronomical calculations and some follow certain other Muslim countries. Each of these has different approaches to doing so; for example, regarding the sighting of the moon, there are three criteria:

  • Sighting the moon using naked eyes after the sunset of the day previous to the first of the month (India, Pakistan, Bangladesh, Morocco, and most Shi'a scholars)
  • Sighting the moon even by using binoculars, etc. after the sunset of the day previous to the first of the month (Iran in some months and the views of some Shi'a scholars)
  • Verdict of the court for the sighting of the crescent upon the sunset of the day previous to the first of the critical months (Saudi Arabia in the months of Ramadan, Shawwal, Dhu l-Qa'da, and Dhu l-Hijja)

Some countries do not have any certain criteria and follow the announcement of the beginning of the month by other countries:

Moon Sighting Committee and Observation Groups

A committee Ayatollah Khamenei established to organize the moon sighting. In 2001, the crescent of Jumada II, 1422 AH (August 2001) was in a position that if Iranian astronomers managed to sight it, several scientific world records regarding the moon sighting would be set for Iran. With the support of the moon sighting committee, a great preparation was made for this sighting and with the success, in that case, sighting groups for moon sighting were established for all months. In certain cases, such as the end of the month of Ramadan, up to 150 groups equipped with advanced optic binoculars around Iran are formed to sight the moon, some of which perform it using airplanes. Every month, this committee announces the reports of its sightings.

Sharia Ruler and the Verdict for Confirmation of the Moon Sighting

One of the ways to confirm the sighting of the moon is the verdict of the Sharia ruler. Although some jurists have accepted this, some have not and have mentioned reasons for invalidity of the verdict of the religious ruler in this issue. According to al-Bahrani, al-Shahid al-Awwal believed that accepting the verdict of the ruler regarding the confirmation of the sighting of the moon is better than refusing it, because the majority of the reasons suggest that if the ruler gives a verdict based on his knowledge which may have acquired from two just witnesses, it is obligatory to refer to his verdict. Al-Fadil al-Khurasani too agreed with al-Shahid al-Awwal, but al-'Allama al-Bahrani also mentioned the possibility of the invalidity of his verdict and mentioned Imam al-Sadiq's (a) statement as his justification, where Imam (a) said, "Regarding the moon sighting, I only permit the testimonies of two just men."


  1. Simultaneity of the moon and the sun refers to the closest distance between the moon and the sun when the moon is between the earth and the sun and is the most difficult state for sighting the moon from the earth. Due to the five degrees of difference between the orbit of the moon with the zodiac, the moon often passes either from above or from below the level of the sun. Sometimes, this simultaneity happens in a way that the moon passes exactly in front of the sun when the solar eclipse takes place.
  2. Zodiac is a belt on which the sun, the moon, and planets pass, from the eyes of an observer on the earth.


  • The material for this article is mainly taken from رؤیت هلال in Farsi WikiShia.