THE LONGEST “BLOOD moon” eclipse this century began this evening, but many Irish stargazers are being hampered from seeing the thrilling celestial spectacle as a cloudy night pervades across the country.

As Mars is the closest it’s been to Earth in 15 years tonight, it’s a double whammy for keen amateur and professional astronomers alike.

In Ireland, the eclipse is set to last for about 3 hours and 6 minutes, from 9.22 pm to 12.28 am.

The period of complete eclipse — known as “totality”, when the moon appears darkest — lasted for just under 51 minutes in Ireland, from 9.26 pm to 10.13 pm.

David Moore, from Astronomy Ireland, told TheJournal.ie that he was hoping for a break in the clouds before the opportunity passed this evening.

Fortunately for those who not be lucky enough to see the moon tonight, they will get another chance for a visual feast in the not-too distant future according to Moore.

“We are actually set to get another eclipse on 20 January next year,” he said. “We’ll get to see the whole thing from start to finish.”

What is a blood moon?

A total lunar eclipse happens when Earth takes position in a straight line between the moon and sun, blotting out the direct sunlight that normally makes our satellite glow whitish-yellow.

The moon travels to a similar position every month, but the tilt of its orbit means it normally passes above or below the Earth’s shadow — so most months we have a full moon without an eclipse.

When the three celestial bodies are perfectly lined up, however, the Earth’s atmosphere scatters blue light from the sun while refracting or bending red light onto the moon, usually giving it a rosy blush.

This is what gives the phenomenon the name “blood moon”, though Mark Bailey of the Armagh Observatory in Northern Ireland said the colour can vary greatly.

It depends partly on “how cloudy or transparent those parts of the Earth’s atmosphere are which enable sunlight to reach the moon”, he told AFP.

“During a very dark eclipse the moon may be almost invisible.

“Less dark eclipses may show the moon as dark grey or brown… as rust-coloured, brick-red, or, if very bright, copper-red or orange.”

With reporting from AFP