Eastern beaches the best place to view the moon turn blood red - providing the weather is good.

Classrooms next week will be abuzz with excited chatter about a blood-red moon.

A child-friendly lunar eclipse - where the Earth passes between the moon and the sun, casting a red glow on the moon - will be seen before bedtime on Tuesday evening.

Forecasters say the best chance of viewing the astronomical extravaganza is by perching high on an eastern beach sand dune and hoping bad weather holds off.

It is the first of two lunar eclipses to be seen from New Zealand this year, with the second event happening around midnight on October 8.


But Tuesday's eclipse will be a special family affair.

"The big attraction is after dinner time and families can go out together and have a good look," said David Britten, astronomy educator at Stardome Observatory at Auckland's One Tree Hill.

Spectators will be able to see the moon rise from 6pm.

It will then move within the Earth's shadow to be eclipsed by 7.08pm - about 15 degrees above the eastern horizon.

The full eclipse will last for one hour and 15 minutes.

In a lunar eclipse, the moon is obscured as it passes through the Earth's shadow.

Two shadows will cross the moon during the event - the large penumbra (or "almost-shadow"), which dims the moon, and the umbra, a smaller opaque shadow caused by the Earth blocking out the light from the sun to the moon.

And the best vantage point, according to both astronomers and meteorologists, will be on any eastern beach - if the clouds stay away.

MetService forecaster Daniel Corbett said early indications have a weather system lashing the west coast on Tuesday.

But eastern areas, particularly Gisborne, Hawkes Bay, and eastern Bay of Plenty, might stay dry, and clear, for long enough to see the event.

"Even if there is cloud and rain forecast, you might just get a break in the cloud to see it," Mr Corbett said.

The moon would appear blood red, Mr Britten said, but in built-up areas with artificial light, it would be a more bronze colour.

He advised a quick reconnaissance mission the night or two before the eclipse to see where the moon would be rising and to check there were no obstacles - trees, hills, buildings - blocking the view.

Members of the Auckland Astronomy Society will be gathering at Browns Bay, Cheltenham Beach, Eastern Beach, One Tree Hill and the Arataki Visitors Centre in the Waitakere Ranges.