For astronomers and interested onlookers today will be spent either scrambling for a telescope and eye protection wear or cursing the clouds and overcast conditions as many attempt to witness the transit of Venus.

Over six hours, depending where in Australia you are located, Venus will move in front of the direct line of vision of the Sun. See ABC Science for transit times.

The transit of Venus occurs in pairs with the last transit eight years ago, after Wednesday venus won't be seen in front of the sun for another century.

The transit was once used as a measuring tool to gauge the distance between the Earth and the Sun but now the event will be useful in exploring events beyond the solar system says professor of physics - Dr Roger Clay.

"There will be people who are interested in transits around other solar systems and they'll be able to use this transit as a way of testing their techniques for observing things like this," he said.

As a student and teacher of physics for several decades Roger said there are still many things intriguing about the study of space and science exemplified in the upcoming transit.

"It will be the final time in all our lifetimes... it's quite fascinating just to see this dot move across the surface of the sun.

"It always seems a bit miraculous that our picture of our solar system just keeps working and to see Venus move across the face of the sun is pretty impressive actually.

"I think astronomy is really good for getting anybody interested in science, many of us are interested in the universe out there and to actually go to a telescope and be able to see magical things like this is exciting for many of us I think.

"It's a good thing and does encourage people, and schools will be talking to students about it so it all works together I think to encourage people to get more of an interest in science," he said.

Roger says astronomical events have fascinated people for thousands of years.

"Ancient people knew a lot about the skies - more than the general public in Australia currently know because we have street lights and many of us just don't go out and notice what's happening in the sky.

"They understood the skies really well from a general visual viewpoint so they built their society very much around astronomy so it's very interesting for me to understand their relationship with the skies.

"Those early people knew where to expect Venus to be ... ancient people were very familiar with Venus... people often argue structures such as the pyramids reflect that knowledge," he said.

Around Australia many will be attempting to observe the transit of Venus.

In Broken Hill, space observer enthusiast Trevor Barry will be at fever pitch in anticipation of the transit.

The unpolluted and often clear skies of far west New South Wales have frequently provided Trevor the opportunity to use his powerful backyard telescope to observe events in the solar system.

For Trevor the event will be special for its historical connection.

"It's far more than just a rare astronomical event, this is crucial to the history of astronomy and the history of Australia," he says.

The event has strong historical context with the transit of Venus being a key reason for Captain James Cook's voyage to the Pacific Ocean which inevitably lead to his fleet encountering Australia in 1770.

"When Cook got back to Europe a French mathematician, Lalanne, using Cook's data, calculated the Earth-sun distance to be 153 million kilometres," he says.

Trevor says this number, while not exactly correct, was within five per cent of the modern understanding of the distance between the Earth and the Sun and despite that, Cook's contribution to the world of science is often overlooked.

"If Cook didn't get that data, it would have been another hundred years before scientists knew the size of our solar system.

"His contribution to science is right up there (but he) never gets the recognition," Trevor says.

During last pair of viewable transits in 1874 northern Tasmanian town of Campbell Town welcomed the US Navy.

The US Navy team were diverted from their original destination of the Crozet Islands and made their way to Hobart where another Navy team were already in location at the Angelsea Barracks.

Leader of the second group, Captain Charles W. Raymond, was invited to travel up to Campbell Town to make his observations there.

They based their temporary observatory at a property in the centre of the town.

Recently, a handmade Union Jack flag that was given to the party by the people of Hobart in 1874 has made its way back to Tasmania.

Campbell Town will again host astronomers and curious onlookers alike for the observation of this transit of Venus.

The telescopes will be set up at the Campbell Town Showgrounds, and weather permitting, members of the public will be able to safely view projections of the transit.