Once in a lifetime eyeful of Venus
IT'S A twice-in-a-lifetime moment.
Tomorrow morning, an event that takes place only four times every two centuries will enthral the world's astronomers, as it has since the 1600s.
People all over the world will be craning their necks to get a look at one of the rarest sky events possible, the Transit of Venus - and nobody alive will see this again. The next one will be in 2117.
Well-known Australian astronomer and writer for Australian Science magazine Dave Reneke said Australia, New Zealand, East Asia and the western Pacific were the best locations for viewing all of the 2012 transit, which started soon after sunrise and finished in the afternoon.
People in the United States will be watching for it this afternoon. Most other parts of the world will see some of the transit, with the exception of West Africa and most of South America.
"A transit of Venus is when the small disc of Venus passes in front of the Sun," Mr Reneke said.
"The event takes several hours and has only been viewed six times in recorded history.
"The last was in 2004 and was watched by millions who used tele
scopes to project images of the Sun's disc and the dot of Venus on to cards or electronic monitors."
Mr Reneke said the reason Lieutenant James Cook came to the southern hemisphere was to view the transit of 1769.
"By comparing northern observations astronomers of those times were able to calculate the distance between the Sun, Earth, and Venus," he said.
"It was pretty accurate. Then he went on to discover Australia."
Scientists hope the 2012 transit will give them more clues about the atmosphere of Venus plus provide priceless data in the hunt for habitable planets in deep space using similar transit methods.
You can view the Sun directly by using specially made filters. Do not use sunglasses, smoked glass, exposed film or CD/DVDs as filters.
While these objects may reduce the amount of visible sunlight they don't reduce the radiation. Eye damage could be the result.
Mr Reneke's website davidreneke.com has free fact sheets and other downloadable information on the history of the transit and how to watch the transit safely from any city in the world.