It is an astronomer’s dream and has not happened since 1982 – a ‘supermoon’ lunar eclipse.
In the early hours of Monday morning, a full moon will coincide with a lunar eclipse, when the earth blocks the sun’s light from hitting the moon.
It will also be a lunar perigee – or ‘supermoon’ – when the moon is at its closest orbit to earth, making it look up to 14% larger than normal.
“Supermoon is not a scientific term, it’s probably a bit of sensationalism” said David Moore from Astronomy Ireland.
“But anything that gets people looking at the moon is a good thing in our books.
“Someone took the illusion of the moon being bigger and coined the phrase, but whether you would notice it yourself is another thing.”
This particular eclipse is also known as a ‘blood moon’.
“It is very rare for those elements to come together – it’s a special event,” said Terry Moseley from the Irish Astronomical Association.
“Few people have seen a lunar eclipse, especially as it happens in the early hours of the morning or it’s too cloudy. Sometimes it’s simply not visible from Ireland.
“It will turn a glorious colour – orange to deep red – depending on the light from the edges of earth’s atmosphere.”
There were just five instances of such a celestial event in the 20th century, and if you miss this one, the next is not until 2033.
The crucial question is will the weather give clear sky? High pressure will keep it dry, but some cloudy conditions are forecast at the minute.
“During cloudy eclipses in the past someone, somewhere in Ireland has seen a break in the cloud and has taken a great photo,” David Moore said.
“I’m sure that will happen again if it’s cloudy this time.
“Take the morning off work and go out and see.”
The eclipse begins at 03:11 BST, will peak at 03:47, and will end at 04:23
Astronomy Ireland are running an Eclipse Watch event from 2am to 6am at its Dublin headquarters, and says “everyone is invited to come and watch the event, view it up close in binoculars and telescopes, and take photos even with your smart phone”.
It has been more than 30 years since a supermoon combined with a lunar eclipse, according to NASA.
The next total lunar eclipse will not be until 2018.