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He it is that cleaves the day-break (from the dark): He makes the night for rest and tranquility, and the sun and moon for the reckoning (of time): Such is the judgment and ordering of (Him), The exalted in power, the Omniscient. It is He Who makes the stars (as beacons) for you, that you may guide yourselves, with their help, through the dark spaces of land and sea: We detail Our Signs for people who know. (The Qur’an 6:96, 97)
With these Ayat of the Qur’an, Allah has given us a mandate to understand the heavenly bodies as part of our worship. For it is obvious from these Ayat that the position of the earth with respect to the Sun and the Moon control the timing of our Ibadaat. The sun for Salat and Saum timings and the moon for the months. Unfortunately, every year, we are not among the people who know, nor those who can tell time, and stumbling through darkness we suffer every Islamic holiday in confusion, disunity and, ultimately, our own spiritual undoing.
Islamic months begin at sunset on the day of visual sighting of the lunar crescent. Even though visual sighting is necessary to determine the start of a month, it is useful to accurately predict when a crescent is likely to be visible in order to produce lunar calendars in advance and to guide the watchers where to look. Since ancient times, many civilizations and astronomers have tried to predict the likelihood of visualizing the new crescent using different 'minimum visibility criteria'. This should not be difficult as Allah has created the solar system subjected to precise calculations:
… The sun and the moon (are subjected) to calculations. (The Qur’an 55:5)
Astronomy has been called the "queen of sciences". It incorporates many disciplines such as physics, particularly optics, mathematics and celestial mechanics. Since ancient times, Muslim scientists have studied astronomy, contributing greatly to human knowledge. Yaqub ibn Tariq, al-Kwarizmi, al-Battani, al-Farghani, al-Sufi, al-Biruni, al-Tusi and Omar Khayyam are just a few of the scholars who have left a lasting mark in the annals of astronomy.
Every year the astronomers, the people who know, publish their calculations that predict the first day of Ramadan or Eid, but mostly many countries start Ramadan or Eid, one day before the predicted day! Is it possible that the astronomers are that foolish to be wrong every year, sometimes twice or even more times a year? Can the astronomical calculations be so inaccurate for crescent sighting and yet absolutely correct for other phenomena? Eclipses occur always at the same instant that the astronomers predict. Occultation’s too. Stars disappear or reappear at exactly the same second that it is predicted.
The sun must not catch up the moon, nor does the night outstrip the day. Each one is traveling in an orbit with its own motion. (The Qur’an 36:40)
Thus the Qur’an tells us quite clearly that the motions of the celestial bodies are fixed and so are the mathematical formulae controlling them. That is why today space crafts can be sent with such precision to explore far away planets in our solar system.
Because of the earth's motion around the sun, the sun appears to move along a path through the sky called the ECLIPTIC. The sun's position on this path (measured from the point where it crosses the equator moving north) is the sun's CELESTIAL LONGITUDE. Each new astronomical lunar month (LUNATION) begins at the moment when the centre of the Moon has the same celestial longitude as the centre of the Sun, from the perspective of the centre of the earth (i.e. the moment when the moon "passes" the sun). This is the moment of astronomical NEW MOON, and it occurs at exactly the same instant regardless of where you are on earth, since it does not depend in any way on the viewer's perspective.
At this moment, when the elongation is said to be 0 degree, the moon is not visible from the earth as it reflects all the sun’s light back towards the sun. After about 18 to 24 hours (on average, one day), the moon moves roughly 12 degrees in its circular motion around the earth, sunlight reflects off its outer edge and, just after sunset the Hilal becomes visible on the earth. That night and the following day are the first day of the new Islamic month.
In the early 1930s, the French astronomer, Andre Danjon deduced that no illuminated portion of the crescent whatsoever can be seen when the moon is 7 degree or less from the sun. No sighting has ever penetrated this barrier, mostly because of the shadows cast by the rough lunar terrain.
The Royal Greenwich Observatory considers 10 degrees as a realistic figure. However, in 1993, in the Quarterly Journal of The Royal Astronomical Society, Schaefer, Ahmed and Doggett, presented a paper entitled Records for Young Moon Sightings in which they have recorded a minimum elongation of the Moon from the sun of 8.1 degree. But this crescent sighting was a rare occurrence.
The subject of crescent visibility has been studied in modern times by a number of Muslim astronomers, both amateur and professional. Several visibility criteria have been developed and even the concept of the International Lunar Date Line (ILDL) has been floated.
With many years of experience, we have fine tuned our criteria of prediction, so that our calculations are borne out by observation time and again. Today our main criterion depends on the moon's angular distance from the sun at sunset (elongation) and the moon's altitude (in degrees) above the horizon after sunset. The age of the moon is recorded as a guideline.
· Elongation at sunset, the Moon / Sun angular separation, should be not less than 8.1 degrees.
· The Crescent must be well above the horizon when the sun has dropped 5 degree below the horizon.
· Crescent age at sunset is normally not less than 20 hours.
These VISUAL sighting predictions assume:
1. Low humidity, haze, dust, pollution.
2. A clear horizon with no clouds near the predicted position.
3. Good eyesight and
4. Searching the correct location on the sky.
The probability of sighting the crescent increases as one travels to the west of this location and diminishes as one travels to the east of it.
Once it has been predicted that the Hilal will be there to be seen, the visibility is further dependent on atmospheric conditions. For although it is possible to calculate the position of the moon in the sky with high precision; it is often difficult to predict if a Hilal will be visible from a particular location. For visibility also depends on weather conditions, atmospheric pollution, the quality of the eyesight of the observer, use of optical aids etc.
Some of the factors affecting Hilal visibility are seasonal, and affect northern and southern hemisphere observers differently because the seasons are opposite. The position of the moon in its orbit can also favor either northern or southern hemisphere observers. (At astronomical new moon, the moon can be as much as 5 degrees North or South of the sun as seen from the earth.)
The seasonal effect arises from the fact that the moon's path makes a much more favorable angle to the Western horizon in spring than in autumn. A smaller effect is the changing time of sunset, depending on latitude. The result is to favor southern observers particularly during September/October and northern observers during March/April.
Many times Muslims have claimed to have seen the Hilal when it was actually invisible. Sightings have been reported for times when the moon had already set, for evenings when the moon set before the sun, and before astronomical new moon, when the moon could only be visible before sunrise! How can this be possible? (Edited version)