Friday, 21 December 2012

Aurora australis shines red in Goldfields

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auroraRed-coloured aurora, like one Mr Goldsmith photographed recently, are caused by nitrogen atoms in an excited state returning to a ground state. Image: John Goldsmith ASTRONOMER and photographer John Goldsmith says the next few months present the best opportunities to photograph aurora australis from Australia.

Otherwise known as the southern lights, the visible aurora occurs when charged particles from solar flares are magnetically funnelled towards the South Pole and react with earth’s atmosphere, emitting photons.

Red-coloured aurora, like one Mr Goldsmith photographed recently, are caused by nitrogen atoms in an excited state returning to a ground state.

Mr Goldsmith, who is a Curtin PhD candidate researching Aboriginal cultural knowledge of astronomy, says he accidentally shot the red aurora while photographing the southern celestial pole at Lake Ballard near Menzies.

He had positioned his camera in the dry salt lake to include the clouds of Magellan, a pyramid-shaped hill, and one of the famous local sculptures by British artist Antony Gormley in his composition.

It was not until later, when he viewed the digital image on screen, that he realised he had also captured the aurora.

Mr Goldsmith says timing and an element of luck are essential for anyone hoping to photograph the southern lights.

“Aurora usually lasts for only a relatively short space of time as viewed from Western Australia, so when it’s occurring maybe part of one evening you might see an Aurora,” he says.

“The second major factor is getting a really dark sky towards the southern horizon.”

He says Perth people should drive at least 70km eastwards to escape interference from the glow of the city, and point the camera towards the south.

He says it is also necessary to have the right equipment.

“A good digital camera, mid to high-end of the range … and a good wide-angle lens that has a wide aperture because for astronomical imaging you need to let in as much light as you can for the exposure to be right,” he says.

“A 24mm wide-angle lens at F2.8 for example, something like that can perform really quite nicely when you are using a good digital camera to go with it.”

“I use a Canon 5D and 40D.”

He says he took the photograph as part of an astronomical photography project called World Night Network.

“We photograph astronomical events of natural and cultural landscapes around the world,” he says.

Mr Goldsmith says we are presently at a favourable time in the 11-year solar cycle to see more manifestations of aurora australis, particularly over the next 6-12 months.

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