Cold Moon: How to see longest full moon of the year this weekend

Best time to see next full moon in the UK is in the early hours of Sunday morning, though it will still appear full on both dates either side of peak

The full moon on 18 December will take place on one of the longest nights of the year (Getty Images/iStockphoto)

This weekend’s full moon will take place on one of the longest days of the year, offering sky gazers a unique opportunity to appreciate the celestial spectacle.

The Cold Moon, so-called because this is how December’s full moon was known by Native American tribes, is the final full moon of 2021, reaching its peak fullness at 4.35am on 19 December.

It comes just three days before the Winter Solstice, which marks the shortest day of the year in the Northern Hemisphere.

“As the full Moon closest to the Winter Solstice, this will be the Long Night Moon,” Nasa states on its website.

“The plane of the Moon’s orbit around the Earth nearly matches the plane of the Earth’s orbit around the Sun. When the path of the Sun appears lowest in the sky for the year, the path of the full Moon opposite the Sun appears highest in the sky.”

In the UK, the sun will set before 4pm and rise after 8am, making the night skies longer and darker than any other point in 2021.

The Moon will seem particularly big as it rises in the evening and sets in the morning, as its proximity to the horizon creates an optical trick known as the Moon Illusion.

This is where the brain is tricked into thinking that the Moon is larger when compared with the relative size of objects on the horizon, such as buildings and trees.

There is no solid science behind this theory, with Nasa explaining that it most likely has something to do with the way we visually perceive the world.

“There’s some thinking that objects in the foreground of your lunar view play a role,” the US space agency explained in a blog post. “But this isn’t a perfect explanation. Nasa astronauts in orbit also see the Moon Illusion, and they have no foreground object to act as distance clues. So there’s likely more going on.”

The Moon will appear full to the casual observer from Friday night through to Sunday night, with parts of the UK offering ideal weather conditions to view it.

Weekend forecasts from the Met Office suggest northern parts of England and Scotland will be treated to the clearest skies.