By Tariq Muneer from Edinburgh Napier University
The world Muslim population has crossed the 1.8 billion mark or 25% of all humans. There are tens of millions Muslims who have acquired higher education. Yet, one problem that has dogged the Muslim Ummah for many decades is the issue of reliable moon-sighting.
Each year arguments ensue amongst mosques on the validity of date, mainly, for the start of Ramadan. Solution exists for the latter problem which may be based on the principle of Imkan-eRuyah or probability of sighting the moon. Under that principle the earliest date for sightable moon may be obtained for any given location and month and any claim for moon sighted may be questioned and rejected. In this respect a team of eight astronomers has this year (2024) published a landmark article that needs to be discussed by authorities who determine the start of the lunar month. The referred article, Assessment and review of modern lunar crescent visibility criterion, was published in the Elsevier’s Icarus journal issue 412, 115970, 2024. A summary of the article is presented here.
Note: The article is highly technical in nature and a good grasp of college-level mathematics would be a precondition to completely grasp the underlying discussion.
First of all it is easily possible to use astronomical calculations to ascertain whether the crescent moon is above the horizon of the viewer. That condition is known as Wujudul Hilal.Any sighting report under condition of the absence of Wujudul Hilal ought to be rejected.
The next condition is the Wujudul Hilal.
The article presents an historical account of the relevant developments that have taken since before Christ (ancient times, observations being reported by Babylonians and Hindus), medieval times (the work of Khawarizmi, Qallas, Lathiqi, Sanjufini, Yunus and Maimonides) and modern astronomers from twentieth century (Danjon, Fotheringham, Maunder, Bruin, Ilyas, Yallop and Odeh).
Note that all but one of the medieval scholars was Muslim who have contributed very significantly towards developments in astronomy. In this respect another work of note is the doctoral thesis of Fatoohi published in 1998 by Durham University, England.
Returning to the article under discussion which is based upon the largest yet dataset of moon sightings we note that 8,290 sets were used of which 5,267 were positive records of sighting and 3,023 negative records, i.e. attempts were made to sight the moon with negative results.
Of the positive sightings, 4,092 were naked eye sightings (which would be the basis for determining the start of any given lunar month), 1,175 positive records using optical aids (such as still and video cameras and telescopes).
The seven astronomical parameters that are used in determining the earliest possible sighting of lunar crescent are: (i) moon age since its birth for any given month, (ii) lag time which is the interval between sunset and moonset, (iii) altitude difference between moon that exists above horizon and the sun that has set, (iv) the elongation angle between the centres of set sun and above-horizon moon, (v) the azimuthal difference between moon and the sun, (vi) moon’s altitude, and finally, (vii) the width of the lit area (arc seconds) of the crescent measured along moon’s diameter.
The article, aided by suitable figures and tables, presents the interaction of above parameters and the minimum conditions for lunar crescent sighting (Imkan-e-Ruya). However, after a careful review of the article the most important deduction one obtains is that despite all the modern developments the simplest solution is to follow the Hadith which dictates us to sight the moon to start and end the Islamic month. Subhan Allah!
Tariq Muneer is PhD, DSc, CEng, MIMechE, FCIBSE, Millennium Fellow Edinburgh Napier University, UK t.muneer@napier.ac.uk
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