THE Clarence Valley skies will offer a magnificent opportunity to watch a once-in-a-lifetime phenomenon tonight, when a lunar eclipse coincides with a super blue moon.

Steve Fletcher from the Clarence Valley Astronomical Society explained that a blue moon was when there are two full moons in a calendar month.

At the same time, there will be a super moon, when the moon is closest to the earth and appears larger than normal.

The lunar eclipse is when the sun, earth and moon align and the moon gives a reddish colour as it passes directly through the earth's shadow.

"The trajectory of the moon around the earth is not a perfect circle," Mr Fletcher said.

"There are times when it is further away and there are times when it is a lot closer. This will be one of the times when it is a lot closer."

At its closest the moon will be 360,226km away, compared to 405,700km on January 16. The moon will rise at 6.31pm tonight and set at 5.39am.

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Mr Fletcher said seeing this once-in-a-lifetime event will be all weather dependent. If the sky is clear, it will be a sight you won't want to miss.

"I always like to find a nice high headland overlooking the ocean, or the top of a hill or mountain top," he said.

"Somewhere where you have a clear view of the horizon."

Mr Fletcher said the Maclean Lookout or Waterview Heights would be brilliant spots to see the super red blue moon.

The forecast is for possible showers.

WHEN TO WATCH:

THE super red blue moon starts at about 10.48pm tonight in the Clarence Valley, eclipsing fully from 11.51pm to 1.07am, and ending at 2.11am.