Southland stargazers are hoping the weather will not hamper viewing the Transit of Venus tomorrow.
The rare event, which means the planet Venus passes directly between the Earth and the Sun, will be visible from about 10.30am - provided it is not cloudy.
The next transit will not occur until 2117.
Southland Astronomical Society president Steve Butler said the forecast was not encouraging but he hoped it would clear up for some of the day.
He would be setting up his telescope, equipped with a sun filter, in Wachner Place provided the weather was kind.
"You will be able to see things like sunspots on the face of the Sun as well as Venus itself," he said.
Other astronomers would be bringing binoculars so the transit could be projected on to paper for safe viewing, he said.
The planet will be visible as a small black dot on the solar disc for several hours.
Mr Butler said if the weather was not good in New Zealand there would probably be websites where the transit could be viewed.
Transits occur in pairs eight years apart – the previous one, not visible from New Zealand, was in 2004.
The pairs happen in a cycle separated by gaps of 105 and 121 years. The previous pair occurred in 1874 and 1882.
There is a great deal of scientific history behind the transit.
It was used as a method of measuring the distance of the Earth from the Sun during the 17th and 18th centuries.
But to get an accurate measurement, astronomers in several different places on the globe coordinate their efforts, first possible in 1761.
Observing the Transit of Venus in 1769 was one of the objectives of Captain Cook's first voyage to the Pacific, during which he mapped the coastline of New Zealand and east coast of Australia.
HOW TO VIEW IT
From 10.30am till 4.45pm tomorrow
Use a pair of binoculars to project the Sun on a piece of paper or cardboard
Use a pinhole in a sheet of paper to project on another surface
Do not look directly at the sun unless you have a telescope with a solar filter.
Sunglasses are not safe.
- © Fairfax NZ News
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