The supermoon is seen in Qinhuagndao, northern China's Hebei province, November 14, 2016. [Photo/Agencies]

On Monday, the full moon's relative proximity should make it appear about 14 percent bigger and 30 percent brighter than at its furthest orbit point, according to the Irish Astronomical Association.

"Because the Earth/moon system will be getting quite close to the time of year when it is closest to the sun (Jan 4, 2017), the moon will be receiving more sunlight than average, also boosting its apparent brightness."

Furthermore, the moon's position in the sky will mean its southern hemisphere, the brighter of the two, will be turned toward Earth, said the IAA.

Without foreknowledge, one might barely notice that the moon appears brighter than usual, astronomers say. Once it is high in the sky, it would be hard to tell that the moon is larger.

But on the horizon, it could be quite spectacular.

"When you look at the moon when it's rising, there is this optical illusion where it looks bigger," said astronomer Mark Bailey, emeritus director of the Armagh Observatory in Northern Ireland.

One every 14 months

Lying low, as a backdrop to trees or buildings for context, our satellite appears larger to the human eye despite being the same size the whole night.

Supermoons are actually not uncommon - there is one every 14 months on average.

"But some supermoons are more super than others," said Pascal Descamps of the Paris Observatory - the closer the Earth the more so.

"If you want to try to image it, choose a location where you'll get some nice terrestrial feature in the foreground: a well-known landmark such as a tower or a spire will provide a nice comparison, particularly if you stay back a bit and use a zoom or telephoto lens which will magnify both objects," added the IAA.

The next comparable event will be in 2034, when the moon will come even closer, by 64 km, to Earth.