MOST Australians probably don't realise the significance to Australian history of Venus moving between the sun and the earth.
In 1769, then Lieutenant James Cook was in Tahiti, ostensibly to observe the transit of Venus across the sun from the southern hemisphere in the European race to measure more accurate astronomical data.
With that job done, Cook opened a sealed envelope with secret orders from King George III.
Cook was instructed to sail west and attempt a discovery of the fabled Terra Australis Incognita, preferably before the French or Dutch could do so.
He subsequently sailed via New Zealand and up our east coast in 1770, setting anchor in and naming Byron Bay, sighting Wollumbin (and naming it Mt Warning), after making landfall at Botany Bay.
It was this discovery of Australia's bountiful east coast that led to British colonial settlement of the country, so the timing of the 1769 transit of Venus has a special place in Australian history.
The transit is one of the rarest astronomical events, occurring twice in quick succession every century or so: since 1769 there have been only three transits, a pair in 1874 and 1882, and the most recent in 2004.
After the upcoming transit on June 5-6 it won't occur again until 2117.
These days, the transit remains of vital importance to astronomers, particularly in their attempts to discover "exoplanets" or planets outside the solar system.
Astronomers use the same "transit method" for observing Venus moving across the sun to observe planets in other systems light years away moving across their respective suns.
Since 1995, 700 planets have been discovered, contributing to scientists' hopes that there may in fact be earth-like planets out there.
Leading astronomer Dave Reneke of Australasian Science Magazine said northern NSW had some of the best skies in the world for viewing such phenomena, given the frequent clarity of our autumn and winter skies.
The transit begins at 8.15am and ends about six hours later, so there's plenty of time to get a view.
But Mr Reneke issues a warning - never look directly at the sun - the transit can only be viewed using special equipment such as solar glasses.
Fact sheets on the transit and how to best view it can be downloaded from Mr Reneke's website at http://www.davidreneke.com.
Chairman of the North Coast Institution of Surveyors Neil Kennedy has also invited schools wishing to arrange a viewing of the transit to apply for a special telescope for the event.
After purchasing 20 scopes they have about nine left and are happy to present the scopes along with tuition from a qualified surveyor in time for the transit.
For information, call Mr Kennedy on 02 6687 4700.