Aurora Australis from Lake Tekapo - New Zealand
- Fraser Gunn Astrophotography -

All of these image have been taken from around the Lake Tekapo area (Aoraki Mackenzie Dark Sky Reserve), to see a larger size please just click the image you want to see



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How to take a Photo of the Aurora

If your the lucky one to be in the right place when the Aurora is active, taking a photo of it is quite simple, all you will need is a camera with manual control (so you can control both the shutter speed and aperture at the same time), high ISO and with manual focus (basically any SLR type will do), a wide angle lens with a large aperture (the expensive part), tripod and a shutter release cable or remote. Every time I have seen the aurora it has always been moving quite fast so sadly you are restricted in the fact that if you want the aurora to look sharp you are going to have to take a fast photo (relative to night photography) otherwise the aurora will end up being a smug across your photo with no distinctive rays and you could have slight startrails. Once you have the gear out, the hardest thing to do is get the focus correct, sadly auto focus most probably will not work, so point the camera towards a bright star and while looking thou the camera "take your best guess" now if you have live view/focus turn that on and digitally zoom in on the star and change the focus until the star is looking the sharpest (usually very easy to do and should only take you a maxium of 30 seconds) if you didn't have live view/focus then sadly you are going to have to take many photos and between each photo (10 seconds should do, ISO 6400, aperture wide open) compairing it to the one before and then making the appropreate adjustment, step by step until you get it right - if you can get focus within a couple of minutes then you are doing well. If there is a moon in the sky you can try auto focus on the moon (sometimes this works) if this works remember to change to manual focus before you start your aurora image. Once you have focus (don't change it!!!) point the camera towards the area that appears to be the most interesting and take the exposure (lenses F/1 - 2.8 should only need between 5 to 20 seconds depending on how bright the aurora is) sadly lenses that don't have a large aperture are going to require a longer exposure of up to 90 seconds or more, even if there is just some strange glow in the distance that you can bearly make out with your eye, take a photo, because of the timed exposure your camera will detect more light and colour than you can see with your eye - hopefully you will supprised when you see the result on the LCD screen. If you are not taking an animation (sequence of photos) it is usually best to use the on board noise reduction, high ISO / long exposure noise reduction. On almost all cameras this will take up as much time as you exposed for (if you take a 25 second exposure, you will have to wait another 25 seconds for the noise reduction) but will mean you will have a less grainy image to work with afterwards.

Aurora Australis

This is the name of the southern lights often seen at the lower latitudes of New Zealand on a clear dark night. The phenomenon begins at the sun where a particularly large coronal outburst creates a strong stream of charged particles known as the solar wind. The solar wind interacts with the Earth's magnetic field lines at the altitude called the magnetopause and the charged positive and negative charges are then associated with the Earth's magnetic field, creating a large charged electric field concentrated at the poles. In the southern hemisphere the field lines are streaming out of the Southpole which is like a north pole of a magnet. Current flows between these electrical polarities, through the ionosphere, across the polar region and back. The streams of electrons which are the negatively charged particles are flowing - spiraling, along the magnetic field lines and intercepting the oxygen and nitrogen atoms in the upper atmosphere. These excite the oxygen and nitrogen atoms causing them to fluoresce, just as they do in a conventional neon fluorescent light tube. The only difference is the excited oxygen atoms emit a greenish white light, and the nitrogen molecules which are excited by more energetic electrons are made to emit the red to pinkish colours. Ionised nitrogen gives off a blue violet light. The light emission or fluorescence from atoms is caused when electromagnetic energy strikes an atom raising the electron orbital level to a set, higher energy level, which may then collapse back again emitting a photon of light of a particular wavelength. This determines its colour.
(Written by Peter Cattell 31 May 2005)

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Fraser Gunn & Yuriko Yoshino, 68 School Road, Fairlie, New Zealand