Last year's solar eclipse, as seen from Palm Cove, Cairns. Photo: Peter Rae
In November 2012, far north Queensland witnessed one of the most intoxicating natural phenomena we can see from Earth - a total eclipse of the sun. It occurs when the moon is between Earth and the sun, totally obscuring sol from our view and casting a deep shadow on Earth's surface, resembling late twilight along a path about 150 kilometres wide.
Not all eclipses are the same, however. Because the moon's orbit is elliptical, not circular, the longest eclipses occur when the moon's course brings it nearer to Earth, making it look a little larger and taking longer to move over the sun.
Conversely, when the moon's orbit takes it to its furthest point from Earth, its size in the sky appears a little smaller to us.
Should an eclipse of the sun occur with the moon at this position, its size is not large enough to totally cover the sun, leaving a very thin ring of light - or annulus (Latin for ''ring'') - around the outside of the moon's disc. It might not be as remarkable as totality, but it's a wondrous thing to observe nevertheless.
Such circumstances bring us an eclipse this Friday morning. It follows a similar path to November's, but the centre line is about 250 kilometres north of Port Douglas and its residents will only see a partial eclipse this time. Population centres along the east coast will see less of the sun hidden the further south they are.
In Melbourne it will begin at 7.50am and conclude at 10.02am. Mid-eclipse is at 8.52am and 25 per cent of the sun's disc will be covered. As always, never look directly at the sun unless you are wearing ''eclipse glasses'' or using binoculars or telescopes equipped with the correct filters, or employing projection method.
The Victorian Astronomical Convention (VASTROC) is open to the public on May 18-19. See asv.org.au