Tonight's ‘blood moon' will be the last total lunar eclipse visible in the Bay of Plenty until 2018.

The moon is expected to reflect a deep red colour for almost an hour, from around 11.30pm to 12.30am, prompting the dramatic name.

Tonight will be the last total lunar eclipse in Tauranga until 2018.

But Tauranga Astronomical Society committee president Stuart Murray says the term ‘blood moon' is probably a misnomer.

'The interesting part about it is that they keep talking about the ‘blood red moon', and I suspect it's never that colour,” he says.

'It really just takes the colour from the light refracting through the atmosphere from the sun, and depends on the impurities in the atmosphere, as you get with the sunset. It's the same sort of thing.

'At best it's always sort of an orange, perhaps reddy-orange – but I've never been aware that it's a blood red.”

Stuart says volcanic activity can contribute to the colour through ashy debris ejected into the sky, as could phenomena such as bushfire smoke or sandstorms if they occur high enough.

'But of late I don't think there's been enough volcanic ash in the atmosphere to cause too great a colour,” he adds.

The astronomical event is the second in a series of four total lunar eclipses that will be seen before 2016, and the coincidence has prompted apocalyptic murmurings form societal fringes.

But Stuart is level-headed about such talk.

'Through history people have been a lot more ignorant of what was happening,” he says. 'They took the condition to be something of untold calamity – that something was going to occur – and they couldn't understand it. That favoured the soothsayers of the day.

'Tonight's event is purely the moon going into the full shadow, the umbra, of the earth, and you get the colour caused by light coming from the sun, refracting through the atmosphere of the earth.

In other words, the light is being dispersed, particularly into those sunset-reds, going through onto the moon.

Perseverant stargazers don't need to fear missing out, and the effects should be noticeable to plain eyesight as well as through a pair of binoculars.

'You never know, the weather may clear,” adds Stuart. 'I would suggest, if you have a chance, just come out and have a look around 10.30 this evening.