Moon Sighting
How to sight the new crescent Moon
In the Islamic calendar, the sighting of the new crescent Moon marks the start of the month. Find out how to look for the Moon with the Royal Observatory Greenwich astronomers.
For thousands of years, humans have used the Moon to help mark time and the seasons.
The Moon’s regular cycle in the sky allows people to determine the number of months in a year, keep track of the changing seasons or mark the start of religious festivals.
The Islamic calendar, for example, is a ‘lunar visibility’ calendar.
In the Islamic calendar, a month begins with the sighting of the new crescent Moon. That makes astronomy crucial to Islamic events and festivals, including Ramadan and Eid.
What are the Moon’s phases?
The Moon does not produce any of its light. We can only see it here on Earth because it reflects light from the Sun.
As it orbits our planet, different portions of the Moon’s surface are lit up by sunlight. Looking up at the Moon from here on Earth, the Moon appears to change shape throughout the month. These shapes are known as the Moon’s ‘phases’.
There are eight phases of the Moon, beginning with the ‘new Moon’. This is where the side of the Moon facing the Earth is not lit up by the Sun at all, so the Moon is invisible.
The next phase of the Moon is called a ‘waxing crescent’, where a small portion of the Moon’s surface is lit and can be seen from Earth. This is the phase of the Moon that marks the new Islamic month.
The phases continue to ‘first quarter’, ‘waxing gibbous’ and then ‘full Moon’, where the entire face of the Moon seen from the Earth is fully lit by the Sun.
Then the Moon appears to get smaller, going through ‘waning gibbous’, ‘last quarter’ and ‘waning crescent phases before the cycle begins once more with a new Moon. It takes 29.5 days for us to see the same stage of the Moon in the sky again.
Why is the new crescent Moon important in Islam?
In the Islamic calendar, the new crescent Moon marks the start of a new month.
Although it takes 29.5 days for the Moon to go through all of its phases, it isn’t practical to have half a day for a month. An Islamic month, therefore, can have either 29 or 30 days. How many days each month depends on when the new crescent Moon is first visible.
“On the 29th of each Islamic calendar month, Muslims go out after sunset looking for the Moon,” explains Imad Ahmed, director of the New Crescent Society.
“If you can see the crescent Moon on the 29th, that month has 29 days. If you cannot, it means that the month has 30 days. That’s why, for example, in some years, Ramadan has 29 days, and in others it has 30.”
Predicted Moon visibility maps like the one above can provide a sound scientific guide to when the new crescent Moon may be visible, with the likelihood varying depending on where you are.
The new crescent’s visibility varies worldwide, just as sunset and sunrise times do, so not everyone can see it simultaneously or even on the same day. This variation across the world can lead to some countries marking religious holidays on different dates.
“One of the issues Muslims face in the UK is that we tend to differ amongst ourselves on which dates we celebrate Ramadan and Eid,” explains Imad.
“This is because some Muslim communities in the UK follow the Islamic calendar of other countries. When Muslims in the UK follow the calendars of different countries worldwide, we will naturally have some differences. Different countries might see the Moon on different dates, and different countries might have alternative methods of determining the Islamic calendar, which might not correspond to the visibility of the Moon.”
However, basing the months on the sighting of the new crescent Moon means that anyone can participate. All you need to do is look up!
When is Ramadan? How to sight the new crescent Moon that marks the start of the month
The first day of fasting for the holy month of Ramadan depends on when the new crescent Moon is first sighted.
In 2023, it was visible across most of the Earth on 22 March.
If you want to try and see the Moon, it’s easy. All you need is a clear view of the western horizon where you can see the sunset because the new crescent Moon always emerges near the evening.
Depending on the date, you may want a pair of binoculars or even a telescope, as getting that first glimpse can be tricky. But even if you don’t manage it one night, it should be visible with the naked eye the next.
