Photograph the Aurora

How to observe and take great photographs of the Aurora in the UK

 

THE AURORA BOREALIS, Merry Dancers or Northern Lights

Seeing and photographing the Aurora Borealis is not as rare an event as you might think and in this context I am talking about the whole of the UK, not just Scotland where I am based. I base this statement on having seen and photographed over 350 displays in North East Scotland since 1989. Aurora displays are reported by astronomers and other observers such as pilots and passed to Ken Kennedy, Dave Gavine having retired at the BAAS in Edinburgh and certainly when I have seen them, they are reported in England on a regular basis. The larger displays, although less common, are viewable even south of the Channel. Activity as we move into the next Solar Maximum is beginning to pick up and 2013 are forecast as being the peak of the new Solar Cycle so fingers tightly crossed although there are discussions that it might be a very subdued one relative to historical Maximum's; pray not. The recent display on the 22nd of January, 2012 was the best I have photographed since 2006 was floowed by two even better ones on the 1st and 8th October but since then it has been quiet but in terms of the many displays I have seen these not especially wonderful and I am sure many more and better ones will be seen before long.

For those wishing to see Aurora displays then three internet sites exist that are a must favourite site and the former checked weekly – Spaceweather.com; the others are AuroraWatchUK, operated by SAMNET based at Lancaster University. The former site offers a wide range of space related data but the Aurora information based on Sun surface activity and satellite observations offers predictive information while the Lancaster site is a reactive one, based on magnetometer activity at Crooktree here in Aberdeenshire and both offer a notification service of events happening. The other recently developed UK based on the Moray Coast of North East Scotland is AuroraSpy.co.uk which offers a very useful one-shop stop for UK Aurora information including a very usefl cloud forecast, a very important factor in seeing Aurora displays. Another informative site is the British Geological Survey site with this link to their explanation of Aurora Borealis displays:http://www.geomag.bgs.ac.uk/education/viewing_aurora.html

My knowledge of Aurora displays is based on years of observation and that is the basis of my advice – I am not an astronomer or scientist, skills I wish I had, but as a photographer interested in seeing these fantastic night time events and photographing them, then I can claim a degree of expertise in talking about them.

The Aurora - What are They

To dispel a few myths first: they are not dependant upon temperature i.e. only appearing on cold frosty nights and they are not reflections off the Arctic ice cap. They are caused by activity on the Sun’s surface and outpourings of these highly charged electrons are carried on the solar winds and on occasions come in the Earth’s direction. Some of these electrons manage to get into our upper atmosphere where they collide with gas molecules such as oxygen and nitrogen giving off distinct colours along the same lines as a neon tube. This electrical activity also disrupts the magnetic activity which surrounds the Earth causing the dancing movement so characteristic of Aurora displays as well as causing magnetometers to react and activating the alarm from AuroraWatchUK.

Aurora Borealis [the name for displays in the Northern hemisphere – Australis applies to those happening at the same time in the Southern hemisphere] can therefore occur at any time of the year. I have photographed them in every month and under most conditions from warm to freezing cold, clear nights, between rain showers, through gaps in the clouds, and in light summer nights in July and August in Scotland. They can appear early in the evening, late afternoon in November or only go active nearer to midnight although rarely have I seen one continue through until dawn.

The main cause for our most active regular displays is related to the Sunspots that occur on the Sun’s surface and historically these have been recorded as following an 11 year cycle from peak to low activity, currently coming out of one of the flattest and longest lows on record. Activity is expected to increase over the next few years and maybe at their most active around 2013 and if anything like the early to mid-90’s then on Royal Deeside I was seeing Aurora for three nights in a row, a couple of times a month. In March 1994, I saw Aurora displays for six days in a row although of varying quality and intensity.

WHAT TO LOOK FOR

Given that you have got an indication of a possible Aurora display from Spaceweather.com or perhaps an announcement on the TV weather broadcasts, then firstly you need to have found a viewing area ideally free of any major light pollution and with a relatively clear view to a Northern horizon. During the autumn and winter months the Constellation Ursa Major [The Plough or Big Dipper] gives a good idea of North and in the spring the star constellation that gives the same orientation is Cassiopeia, looks like the letter W made up of five stars. Obviously a compass showing north would be ideal as well and I would check out a convenient viewing area near your home for a few dark clear nights, give yourself 30 mins at least for your eyes to get used to the dark and be aware of what the night sky looks like.

If an Aurora display happens then it is more than obvious, even if a small one and you are only seeing it in the far distance, the probability of colours and movement are a dead give away and are not likely to be confused with spotlights from rabbit shooters over the next hill line. If you watch the sky regularly then often the evening before a display there can be an area of glow, not unlike the twilight just after the sun sets, but given the time of year and latest of the night, such a glow should not be present.

On the evening of a display, one of the first signs is the ARC, a band of light, pale green, blue or yellow and looking like a flat rainbow shape to the North. This can wax and wane; be intense and five minutes later fade until almost non-existence, only to re-appear again a few minutes later. This might go on for a hour or more – once it did nothing else all evening and eventually died out around midnight but usually it will start to go active and large RAYS or beams of light will extend from the arc and can then also begin to move laterally along the arc like searchlights on a trolley being pushed from right to left.

If the arc is particularly powerful it can begin to bend and snake and with multiple rays extending from it gives a curtain like effect, although I have only seen that two to three times. Usually the arc breaks up and then rays start appearing from an amorphous area of light spread across the northern horizon. If it is one of the rarer massively powerful events then the arc can become double and the rays appear to extend upwards to a zenith or centre point directly above the observer and this is the beginning of a CORONA, created as the Aurora display moves southwards over the observer and these are the type of events seen much further south in England. To be underneath one of these is like being under a gigantic coloured golfing umbrella, with a center always twisting and turning and huge sweeping rays of coloured light dropping down to all horizon lines to all points of the compass.

The main colours to be observed in the rays are green, often earlier in the event followed by red and various hues in between – these colours are both from oxygen and changing as the display gets stronger in power, from green to red; occasionally purple colouration is visible, this coming from nitrogen gas. Other colour combinations are visible depending on prevailing weather conditions, air quality, temperature, whether there is a moon, light pollution and also the observer’s individual eye sensitivity. You do not get the light spectrum range of colours as in a rainbow as this light source is only from selected gas molecules.

The most observable qualities that make an Aurora stand out are the scale of the display; it is truly celestial, the colours and the movement and although it can have destructive qualities if very powerful, more on man made electrical systems rather than an individual human being, they are one of the most beautiful and benign night-time weather events to see.

The best weather conditions in which to see Aurora are when you have clear dark cloudless skies – often these occur more in the winter time with long dark evenings and on frosty nights; hence the incorrect association of their appearance only on cold nights or as a winter phenomenon. Big displays are visible in cities, despite the light pollution, if you have acclimatised your eyes to the prevailing light conditions but ideally you want to be in the countryside away from strong pollution if you can.

PHOTOGRAPHING AURORA DISPLAYS

In one sense photographing the Aurora is about as basic as you get – aim and expose. Creatively most of the impact in your final photographs will be determined by the Aurora display itself. As long as you get the basic technique right, the photography will take of itself.

I cannot wait for the next cycle of activity as the camera I have now, a Nikon D700 has an awesome ISO rating reaching 25000 if required but even at its more normal upper level of 6400 its control of noise is probably more superior to my older digital cameras with an ISO maximum of 1600. The ISO capability is very important as the Aurora is a very low light level event so to record acceptable images will require long shutter speeds to achieve well exposed photographs. The faster ISO’s should mean shorter exposures, giving more accurate recording of a moving event but still obtaining well exposed photos.

Past Experience

Over the years of using slide film and then digital from 2002, the best combination with both mediums up-to-now has worked out at a 15-20 second exposure, 1600ASA or ISO and a lens aperture of f2.8. Photographing straight Aurora displays, then f2.8 with the lens wide open had generally not created any problems with Depth of Field or edge sharpness because you are basically aiming at extremely distant object on a relatively flat plain. If however you wish to be more creative such as over a stone circle or building then foregrounds soon become soft [out of focus] and if you focus on a foreground object then for the same reason the background – the Aurora becomes fuzzy. A footnote: slide film is seldom faster than 400asa but with the Fuji film I used the development time could be extended by 2 stops, taking it to 1600asa and the grain still remained acceptable.

Underexposing seemed to be a problem for both film and digital, especially if I just left the camera to expose automatically and with film it was enhanced grain, with digital is it noise and in some cases the CCD structure appeared.  As with any photography it is a compromise between exposure [that must be right], avoidance of camera shake and sufficient depth of field, so the modern digital camera advances all mitigate in improving all the elements. A 20 second exposure is perhaps about as long as you would wish – after that the stars begin to trail or become lines rather than sparkling pinpoints of light, because of the spinning earth; if Aurora are moving and sometimes quite quickly then exposures of under 5 seconds will be wonderful, especially if they are correct exposures.

The chance to have a smaller aperture could mean more depth of field and the chance to be more creative with foregrounds and the best way to give your photographs a greater sense of depth and scale and more interest rather than everything pointing straight at the sky, however spectacular the Aurora display might be.

However saying all that, it is unlikely that you would be able to hand hold your camera and achieve good results however fast you lens might be or advanced the ISO – a tripod will I suspect always be a necessity or failing that a suitable solid surface so any chance of camera shake is avoided. A cable release, preferably one with a locking capability to do timed exposures, is necessary so you can avoid touching the camera. Exposure can be timed using a stop watch, luminescent clock face with second hand or fall back in Gregory’s Girl mode and use one elephant, two elephants etc or 1001, 1002, both of which once practised can given reasonably repeatable time periods. Avoid having to light up a clock face with a torch as it will affect your night vision and of course keep it away from the camera lens.

As I mentioned above an aperture of f2.8 [the widest the lens opens up] was about the best – faster lenses such as f2, f1.8 etc in wide angle lenses were very expensive. You need a wide angle lens, equivalent to 28mm or wider in old 35mm film camera parlance as the Aurora are of such a scale. Many digital compacts to not have a fast lens f3.5, are often not very wide angle and the maximum ISO is seldom more than 800ISO, with noise being a problem at that sensitivity setting, so they are not ideal cameras for photographing Aurora displays. Some do not allow you to attach a cable release and you can even find they have no screw for attaching a tripod so this needs to be checked out long before you have an opportunity to see and photograph an Aurora.

On the night 

The check list would be a camera with suitable lens, ISO set to 1600ISO or above, camera firmly attached to tripod with a cable release in place. If a digital camera then set it to manual with the shutter set to the BULB setting and this allows you to determine your exposure times, open the lens to its maximum and always focus on infinity – sharpest to the far distance.

Spare battery [one at least] to hand, especially on frosty nights and plenty of capacity on your camera card, with spares as well and if you have RAW format then use it so get the best post-production capability; if only JPEGs then select the finest quality for those lovely large prints you will be making.

Assuming you have a f2.8 lens and assuming a 1600ISO, then starting exposing when the display starts: 15 second, then 20 second, then 25 second and start again, maybe in a different position, upright rather than landscape and so on. Doing  a series of exposures covers your options, its is called Bracketing, and if you have a higher ISO to play with then try the same again but maybe starting a 5 or 10 seconds and so on.

Later when you check your photographs on the computer you can refine this for future displays and build up your own experience curve and this will be useful when you see different types of Aurora and can judge the brighter ones where exposure times could be reduced. In general start with adjusting exposure times rather than changing the aperture for once you start stopping down or making the lens opening smaller, then you are cutting the amount of light significantly and shorter exposures will begin to create underexposure and noise. The beauty with a digital camera as you can check in the File Info in Photoshop what your actual exposure times, the ISO and the aperture and soon you will work out the best combination which gives you the most pleasing results for your camera system and your own taste.

As the exposures are long you will find your photographs are more saturated with colour than you probably remember seeing with the human eye but these can be adjusted in your software to suit what you think is accurate. Check out the Spaceweather.com galleries and you find a lot of useful information from other photographers covering many makes of camera and of course wide differences in Aurora displays and locations.

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