Are the calculations of astronomers considered for moonsighting?

ⓘ Supported by Al Medina 313.



Islamic Text

No, astronomical calculations are not considered. This is the position of the Hanafi Madhab as well as others. The Hanafis believe that the Hadith in Sahih al-Bukhari clearly negates calculations for moonsighting.

ابْنَ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا، عَنِ النَّبِيِّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ، أَنَّهُ قَالَ: «إِنَّا أُمَّةٌ أُمِّيَّةٌ، لاَ نَكْتُبُ وَلاَ نَحْسُبُ، الشَّهْرُ هَكَذَا وَهَكَذَا» يَعْنِي مَرَّةً تِسْعَةً وَعِشْرِينَ، وَمَرَّةً ثَلاَثِينَ

Ibn ‘Umar  narrated that the Prophet ﷺ said, ‘We are an unlettered Ummah, we do not write or use (astronomical) calculations. A month is like this, and this.’ Meaning sometimes 29 and sometimes 30 days. (Sahih al-Bukhari , 1913).

The above Hadith has caused Hanafi scholars to conclude that we do not use calculations for moonsighting. In the Hadith the blessed Prophet ﷺ negates calculation for this Ummah (nation). This cannot be a general rule because Islam commands calculations for many aspects of the religion.

For example, we are required to calculate Zakah. We are also required to calculate inheritance. Thus, the Hadith is specific to moonsighting. This is clear from the Hadith since the blessed Prophet ﷺ negated calculation in the context of the Islamic month. Which is based upon moonsighting.

Therefore, the Hadith is understood to provide a specific exception to a general rule. The general rule is that we do use calculations for all aspects of general and religious life. The exception is moonsighting itself. With moonsighting we focus upon testimony. If a testimony is accepted then the moonsighting will be established.

The Hanafi Position
قَوْلُهُ: وَلَا عِبْرَةَ بِقَوْلِ الْمُوَقِّتَيْنِ
أَيْ فِي وُجُوبِ الصَّوْمِ عَلَى النَّاسِ بَلْ فِي الْمِعْرَاجِ لَا يُعْتَبَرُ قَوْلُهُمْ بِالْإِجْمَاعِ، وَلَا يَجُوزُ لِلْمُنَجِّمِ أَنْ يَعْمَلَ بِحِسَابِ نَفْسِهِ، وَفِي النَّهْرِ فَلَا يَلْزَمُ بِقَوْلِ الْمُؤَقِّتِينَ أَنَّهُ أَيْ الْهِلَالَ يَكُونُ فِي السَّمَاءِ لَيْلَةَ كَذَا وَإِنْ كَانُوا عُدُولًا فِي الصَّحِيحِ

No consideration is given to the opinion of astronomers. Meaning with regards to obliging fasting upon the people. Rather in al-Miraaj (the author said) there is consensus (Ijma) that their (astronomers) opinions are not considered and it is not permitted for a starwatcher to act according to his own calculations. In al-Nahr (the author stated) it is not binding to act upon the opinions of astronomers when they say the crescent will be (visible) in the sky on such a night, even if they (the astronomers) are upright, according to the sound opinion. (Imam Ibn Abideen, Radd al-Muhtaar).  

In the above Nass (text), not only does Imam Ibn Abideen present the Hanafi position on using calculations, but he also claims consensus (Ijma) upon it. He further explains that calculations are not to be used even if the astronomers making the calculations are reliable.

Despite the clarity of the Hanafi texts in negating calculations for moonsighting, we often find many western Hanafi institutions and teachers using astronomical calculations to negate an established moonsighting. If they are doing this based upon another Madhab then they should clarify this to their congregations. Without such clarification they cause widespread confusion.

Generally, this is not the approach of Hanafis in the Muslim world. Rather they tend to follow the Sunnah method when it comes to moonsighting. They do not tend to use calculations for moonsighting.


The Hadith is clear and the position of the Hanafi Madhab is clear. We do not use calculations for moonsighting. People who oppose this view must provide evidence to show why they do not follow the Hadith. They must also provide references from classical Hanafi works to demonstrate that they are representing the Hanafi position correctly. Without doing so, their arguments will be disregarded.

It is important to emphasise that the Hadith above is not considered to be general and consequently applicable to all aspects of life, rather it is specific to moonsighting. Therefore, we do use calculations for other matters but not moonsighting itself. Since the Hadith is clear in negating calculations for moonsighting.

And Allah (Most High) Knows best.

– Answered by Shaykh Noorud-deen (08.04.2021)

See also:

Is the Hadith about not using calculations for moonsighting Sahih?

Does taking an injection invalidate the fast?

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