Another Ramadan has departed us, and similar discussions have again occurred in our communities. Towards the beginning and end of Ramadan, discussion abounds about the use of moon-sighting “visibility charts” to predict the crescent’s visibility. Many people refer to them decisively to rule in or out the possibility that the moon will be sighted, or to conclusively discredit claimed sightings as spurious or mistaken. But what is the nature of these charts and why is putting stock in their accuracy a problematic commitment to make? Brother Shafiul Haq explores.

There are a couple of important considerations that many of us overlook when it comes to these charts: firstly, the accuracy of these charts, and secondly, their usefulness from a fiqhi perspective.

With regards to the accuracy of these charts, it is important to note that there are different ways to predict the new moon’s first visibility and there is no consensus on any of these methods. Since the moon does not have its own light, there are a number of factors involved in predicting the first visibility of the moon.

For example, according to David King (Frankfurt University) some of these factors include “the positions of the sun and the moon relative to the horizon, the relative brightness of the moon and the background sky, and the prevailing atmospheric conditions.”

Due to these factors, the possibility of sighting the crescent can never be predicted with certainty.


Visibility Charts: the only thing certain about them is their uncertainty.

According to Mohammad Ilyas (University of Science Malaysia), there are two approaches that can be followed to develop a criterion for the first visibility of the moon:

(1) In the observational approach, one needs to obtain data on the crescent’s visibility in the form of positive and negative sightings and parametrize these in astronomical terms…Obviously, this process requires a long observational period and wide global coverage for greater accuracy.

(2) In the theoretical approach, the optical parameters – sky brightness, crescent’s intensity, contrast, etc – are parametrized in the Sun-Moon positions and physical requirements. The method is somewhat complex but, in principle, more accurate and universal.

As Ilyas mentions, the accuracy of the observational approach is dependent on the comprehensiveness of the data collected.

For example, the criterion developed through one of the first studies of this kind was based on data collected mainly from Athens, Greece. Therefore, the accuracy of this criterion when it comes to the visibility of the new moon in other places, especially at higher latitudes, is subject to critique.


Likewise, with the “theoretical” approach, there are a number of criteria that have been developed. One such criterion that used to be popular was the “Danjon Limit”, which estimates the minimum ‘elongation’ for the youngest observable crescent to be 7°. Now, this may not make much sense to the layman but the important point to note is that measures such as the Danjon Limit are not decisive and are subject to change. In fact, the Danjon Limit itself has been revised.

According to Mohammad Ilyas:

…we must recognize that what Danjon had proposed, as a general guide, was an approximate minimum elongation necessary for the young observable Moon. The ‘limit’ is not a sufficient condition and even the revised Danjon Limit, alone, cannot be used as a basis for visibility prediction. This critical difference was overlooked at the 1978 Istanbul conference which adopted a similar…criterion by joining, rather arbitrarily, the old Danjon Limit with a 5o altitude separation…

Regarding the possibility of a scientific approach to determine the earliest visibility of the new moon, Dr D McNally (London University Observatory) says:

…whether observatory scientists have been able to set a standard by which you can be certain of the evening when a new Moon will appear, then I am afraid the answer is no…, one can specify a certain angle but there is always just a chance that someone with particularly keen sight, in a particularly steady and clear atmosphere, might just be able to detect the Moon prior to its reaching its statutory position.

Dr McNally further says regarding the determination of Islamic months through a scientific method:

I am sorry to say there is no scientific way, I think, in which the requirements of Islam can be met at the moment.

Therefore, we need to consider the moon-sighting charts with a grain of salt rather than accept them as absolute truths.

With regards to the usefulness of these charts from a fiqhi point-of-view, it is worth sharing brother Uthman Badar’s comment on this issue which suffices in summarising this second part of the discussion:

…there is no requirement [in Islamic fiqh] to use [moonsighting charts] in the first instance. Although scholars differ on whether they *should* be used to negate sighting claims that are not possible or very unlikely according to the calculations, there is no basis to argue that they *must* be used. This is because the Prophet did not use any such thing. He simply verified testimonies…based on trustworthiness of claimants. This is the sounder method according to most scholars, in which calculations are used neither in establishing sightings nor in negating them.

Thus, both the accuracy of these charts and their fiqhi-utility are not established. To thus premise visibility charts as a given in discussions of whether the moon can be sighted or was indeed sighted by a claimant is to make the error of of giving them a far greater relevance than they deserve. In the no doubt ongoing discussions around moon sighting, calculations, local and global sighting that are likely to continue in our communities for some time to come, it is time to acknowledge the inherently problematic nature of these indecisive charts.

Shafiul Huq is a Melbourne-based activist and member of Hizb ut-Tahrir. He is also a student of Classical Arabic and Cultural Studies.