When the moon rises at about 5pm on Monday it will appear bigger than it has done at any point since 1948.
A rare “supermoon” will make the full lunar disc appear 14 per cent bigger and up to 30 per cent brighter than usual.
The effect is the result of the moon coming closer to Earth than it has done for 69 years. It will be 2034 until it makes a similar approach.
Tonight’s conditions are forecast as breezy and cloudy but the moon should be easy to spot because it will be so large.
Astronomy Ireland said people should go out and view the moon on Monday and also on Tuesday, when it will appear similarly large.
“The chance of every county being 100 per cent cloudy is practically zero,” said Astronomy Ireland magazine editor David Moore.
Optical illusion
According to the society, there will be an optical illusion at about 5pm when the moon is rising that makes it appear even bigger.
“Unlike the supermoon effect, this is not a real increase in size but it is very striking to the naked eye when the moon is low on the horizon, and, of course, with the moon really being 30 per cent brighter, the moon illusion will be all the more spectacular so we are urging everyone to get out and watch.”
Mr Moore said 5pm would probably be the best time to look at the moon because of this illusion (which will also occur early in the morning as the moon sets), but any time during the night should be good.
Indeed, technically speaking, the moon will be closest to Ireland at 12.31am at a distance of 218,614 miles.
Astronomy Ireland will hold a public lecture about Einstein in Trinity College Dublin at 8pm on Monday night which will be followed by a supermoon viewing where attendees will be able to look at the moon through powerful telescopes.
Light pollution
Because the moon is such a large and bright object in the night sky, light pollution and street lamps in urban areas will not hamper viewing – all you have to do is look up.
The moon does not go around the Earth in a perfectly circular orbit, its distance can carry by as much as 14 per cent. A supermoon occurs when the moon is at its closest to Earth.
Monday’s event is the biggest and best in a series of three supermoons. The first was on October 16th and the third is due on December 14th.
Besides looking spectacular, the supermoon will give tides, which are affected by the gravity of the moon and sun, a small boost. High and low tides usually reach their peak during a full or new moon.
