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First find your Aurora. The best website for general awareness of likely activity is Spaceweather.com which, although an American NASA site, gives a few days notice of possible activity which, if large enough, will be seen in the UK. It also has good explanations of what Aurora are, and how they are caused. The site has a map on the left-hand side towards the bottom of the opening page showing likely Aurora display areas. The best UK website, valuable only at the time of likely displays, is AuroraWatchUK. The magnetometer readings for this site come from my garden at Crooktree on Royal Deeside.

For most displays, assuming they are large enough, look toward the North. Avoid light pollution and a high horizon, for example, where mountains are a few hundred yards away. A good star marker in the autumn is The Plough, and in the spring Cassiopeia. A dark, clear sky with plenty of stars and as little cloud as possible is ideal. The eyes acclimatise in about twenty minutes, and it is best not to go straight from computer screen activity. If a display is occurring and active then it will be very obvious. The scale is huge and there will be some movement and colours - mainly green, red and yellow. The full Moon can suppress the clarity of displays but large ones are still visible even if it is included in the photograph.

For basic structures, refer to some of the photographs. AURORALGLOW is often seen on the evening before a display - it appears like twilight when it obviously should be dark. On an active night, anytime after dark, the first sign is an ARC, a pale waxing and waning band of light to the north like a flat rainbow shape. This can pulsate for an hour or so, but if it gets brighter and higher then expect RAYS to break. The most active period will follow with a lot of lateral movement of individual rays, and perhaps dancing and weaving and occasional streaming. Bright patches may also run along the base of the arc or up individual rays. Very strong arcs can fold and bend. If a large event happens, the whole display can spread above the observer. It is then called a CORONA with the zenith or centre directly above, and rays of light falling to all horizons all around the viewer. Strong colours can be associated with this kind of display, and come from high and low level oxygen (red and green) and nitrogen (violet). Many other hues also occur including white and yellow. The colours represented are not those of the rainbow.

After photographing over 300 displays in Aberdeenshire since 1989, using mainly Fuji ISO 400 135 type slide film rated at ISO 1600 and push processed and since 2003, and Fuji S2 and S3 DSLRs, I find that the norm has been an f/2.8 lens wide open, ISO 1600 speed, no filters and an exposure of 15 - 20 second for both systems. The recorded colours are definitely more vibrant than those seen with the human eye, probably because of the over exposures. I would advise making a start here and then adjusting for slower lenses if you have them, with additional bracketing in 5 second blocks.

A tripod and locking cable release are optional but I would suggest are necessary. Generally I use a 28mm or 24mm lens for film cameras (Nikon FM2) but with the DSLR I use a 15mm Sigma fish-eye manual lens and get good distortion free, pin sharp wide angle coverage despite being working at the full f/2.8 aperture. Always focus at infinity. Telephoto lenses are pointless as the scale of Aurora displays is so vast. Binoculars are not required for viewing for the same reason. Slower lenses mean longer exposures, and after 40 seconds star trailing becomes intrusive unless you have astronomical compensation motor drive. Automatic focusing is useless because the scene is too dark. It is best to set the camera to work manually. I find auto-exposures tend to be on the short side, and underexposure noise is apparent with exposures less than ten seconds.

My early photos are all scans from slide film, whereas the 2004 photos were acquired using a Fuji S2. 2005 and 2006 images were captured with a Fuji S3. No S5 results are available yet as no auroras have been visible this year. We are currently in the Solar Minimum period and activity is very quiet. This will hopefully pick up again over the next few years. Remember also that as auroras are often best seen on cold frosty nights (no correlation as a cause) then spare batteries are essential. Use a USB card reader to download cards, not the camera. Bringing the camera indoors can cause condensation. Check for moisture on the lens if the air temperatures changes, and always regularly check the aperture and lens settings if the camera is moved, for example, from landscape to portrait orientation. I have paid the price with both getting changed by accident or inattention.

Artcle by Jim Henderson


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