Transit will open eyes to space magic

It is said that women are from Venus and men are from Mars.

But Northland men will be able to get their own look at our solar system's second closest planet to the sun next month, with the transit of Venus visible over the country - weather permitting.

But those wanting to see Venus passing across the sun on June 6 will have to view the once-in-a-lifetime event through special solar viewers or risk damaging their eyesight.

In what should be a spectacular sight, the planet will appear to be a small ball passing across the face of the sun.

The transit will begin at 10.30am, be at mid-transit at 1.30pm and finish at 4.30pm.

The Northland Astronomical Society will be setting up telescopes for free viewing down at the Town Basin for the occasion.

Whangarei amateur astronomer Don Armitage is among many stargazers who are rubbing their hands in anticipation of the transit, which was last visible here in December 1882.

"I'm really looking forward to it. I've always had an interest in space that was a sparked by the early days of space exploration, so to see a transit of Venus is pretty special," he said.

"It's my only chance to see it here, unless I can be sure to still be alive in December 2117 [when it's next going to be visible from New Zealand]."

Now he's just hoping for clear weather so he can get a good view and Mr Armitage said anybody should be able to see Venus pass across the sun, if the weather was clear, but they needed to do so safely.

He said people could buy special solar viewers from the NZ Astronomical Society (http://www.rasnz.org.nz/Sales/SolarViewers.html) for $2.50 which would let them view the phenomena without risking their eyesight.

Mr Armitage said through the solar viewer the sun would appear to be a large orange disc in the sky. Venus would move across it, appearing as a small black dot, during the transit.

He said trying to view the transit without a solar viewer was dangerous, even if people wear sunglasses.

The solar viewers could also be used to see an eclipse of the sun across New Zealand on November 14.

There are only two planets capable of appearing to us to transit the face of the Sun - Mercury and Venus, as both circle within Earth's orbit.

Mercury, being the closest to the sun, averages 13 to 14 transits per century, always either in May or, more often, November.

Transits of Venus, however, occur in pairs eight years apart, and the period between pairs alternates between 105.5 years and 121.5 years. They occur either in early December or June.

One of Captain James Cook's orders on his first expedition to the South Pacific was to observe the transit of Venus, which he did in Tahiti in the winter of 1769, thus contributing immensely to the accurate calculation of the distance between Earth and Sun, the scale of the solar system (using Kepler's Third Law) and navigation generally.

Sailing up the east coast of New Zealand as far as the Coromandel Peninsula, he anchored in a bay and observed a transit of Mercury in November of that year. Hence the name Mercury Bay and Mercury Islands.