Beyond Moon Age: Factors Affecting Crescent Visibility in the UK [download pdf] [poster image]
Question
Why couldn't we see a 2-day-old moon in the UK in September 2026, but we could see a 1-day-old moon in February 2026 (or even a younger moon in May 2025)? (Question by a London Imam to ICOUK / October 2026)
Answer:
Allah says: (1) "The sun and the moon follow courses (exactly) computed;" (Quran 55:5). (2) "It is He Who made the sun to be a shining glory and the moon to be a light (of beauty) and measured out stages for her; that you might know the number of years and the count (of time)." (Quran 10:5). (3) "They ask thee concerning the Crescent Moons. Say: They are but signs to mark fixed periods of time in (the affairs of) people, and for Pilgrimage." (Quran 2:189)
Therefore, we must accept that the orbit and the visibility of the moon are by the will and design of Allah. We do not have any control over its movements, whether it’s above or below the UK horizon.
Now please note that the moon's age alone isn't an accurate indicator of its visibility in the UK.
From our past moon-sighting experience (2024-2026), we have found that a very young moon (e.g., 18 hrs old) could be easily seen with the naked eye in Spring/Summer, yet a much older moon (e.g., 40 hrs old) could not be seen in Autumn/Winter (even with Optical Aids).
Many factors affect the moon's visibility, such as elongation (how far from the Sun it is) and altitude (how high above the horizon it is), as well as the observer's experience and weather conditions.
Furthermore, in Spring/Summer of 2026, the lunar orbit was over the Northern Hemisphere (with high altitude), so the moon was easily visible, even 1 day before other countries like Morocco.
However, in Autum/Winter of 2026, the lunar orbit is over the Southern Hemisphere (with low altitude), so the moon is not easily visible, even 1 day after other countries like Morocco.
The above fluctuations in the lunar orbit do not happen every year (e.g., 2018 - 2023), but they happen during the Major Lunar Standstills (MSL), which repeat every 18.6 years (e.g., 1987, 2006, 2025, 2043, etc.).
Fortunately, our UK moon sighting data from the past few years of MSL show that the Shariah rule of 29- 30-day months still holds, and so a purely local moon sighting calendar from the UK-only is possible and has been proven to work in the worst case of the low-altitude moons (2024 - 2026).
The only drawback is that there will be a few consecutive 30-day months in the Autumn/Winter, when the moon has very low altitude at sunset, but it makes up the total count by Spring/Summer with a few consecutive 29-day months.
As for the question of unity in the UK, following different foreign countries (Morocco, Saudi Arabia, South Africa, etc.) has not worked over the past 40 years (since 1986).
So, UK Muslim unity is more likely if we adopt pure local moon sightings, even if they differ by 2 days from foreign countries (such as the Saudi Ummul Qura calendar) in some months, especially during MSL! Note also that other countries, like India, have such differences with foreign countries, too (e.g., in September 2026, India started 2 days after the Saudi Ummul Qura calendar1)!
[1] See "Must the UK follow Saudi Arabia?", published in October 2026 [bit.ly/uk2SaudiMoon]
Furthermore, Allah says: "And the Moon, We have measured for her mansions (to traverse) till she returns like the old (and withered) lower part of a date-stalk." (Quran 36:39).
The Tafsir of this verse [Quran 36:39] explains that there are visible phases of the moon when it can be seen, and there are invisible phases of the moon (Mahaq) when it cannot be seen.
Such phases of the moon are shown by the predicted crescent visibility maps below from the ICOUK website (bit.ly/VizMaps).
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| On 27 May 2025 [Dhul Hijjah 1446], an 18-hour-old moon was sighted in the UK (Dewsbury, Leeds, Thirsk, etc.) by many people a day before it was sighted in other countries, like Morocco. | On 15 July 2026 [Safar 1448], a 35-hour-old moon was sighted in the UK (Blackburn, Cardiff, Leicester, London, Slough) by many people on the same day as it was sighted in other countries, like Morocco. | On 12 September 2026 [Rabi-I 1448], a nearly 40-hour-old moon could not be sighted in the UK (as moonset was before or at the same time as sunset in most places), but it was sighted a day later in the UK than in other countries, like Morocco. |
Conclusion: The above crescent moon observation data (with testimonies) from the ICOUK website show beyond any doubt that the age of the moon alone does not determine its visibility but includes many other factors. However, the Shariah rule of a 29- 30-day month is fully met in the UK (since 2018) without following any foreign countries (which may also lead to a 28- 31-day month2), Alhamdulillah.
[2] See "The 1984 Moon Sighting Criteria Review", published in September 2026 [bit.ly/Review1984criteria]
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