Auroral photography: A guide to capturing the Northern Lights

If you've ever been interested in aurora photography, now is a great time to get out there and give it a try. Here's why:

• The activity of our sun (the cause of aurorae here on Earth) ebbs and flows in eleven year cycles.  The peak of the current solar cycle - an apex of auroral activity - will occur around 2013.
  
  
• Revolutionary improvements in imaging technology have been made since the last solar cycle. We have progressed from film to an age of digital image sensors which offer far greater sensitivity and resolution, along with real time feedback and less noise.
  
  
• Our ability to predict the timing and intensity of aurorae has been enhanced considerably with the launch of the Solar & Heliospheric Observatory, the product of a collaboration between the European Space Agency and NASA. 

In the next few years we will enjoy sensational aurorae, advance notice of their arrival, and the equipment necessary to capture them as never before. Even armed with all of these advantages, however, the aurorae are not going to put themselves on your memory cards. That's something you'll have to do yourself, and it can be a struggle. 

This article provides ten suggestions that, if followed, will improve your odds of emerging from that struggle with some exceptional imagery. This article consists of two pages - the first page deals with how to find an aurora and equip yourself to capture it properly, and page 2 will guide you through the remainder of the process, including camera settings, composition and advanced topics.

1. Know Your Subject

Let’s begin by getting to know the aurora. According to my friend, astrophysicist Dr. Henry Throop, the aurora was thought at one time to be caused by ices suspended high above the Earth’s coldest, darkest regions. We now know that the aurora is actually an electrical phenomenon, caused by interactions between the solar wind and the Earth’s upper atmosphere. The sun emits massless photons that we see as light, but also emits out a real, physical, tangible wind of particles which moves at several hundred kilometers per second.

When this wind reaches the Earth, it begins a process that ends by exciting gasses in the Earth’s atmosphere, eventually leading to the emission of light. And just as a true neon light only comes in one color (red), the colors of the aurora are limited too: green and red caused by oxygen, with the fainter blue and purple caused by nitrogen. Unlike the wispy shapes of the aurora, its colors are narrow and precise.

Just like stars, the aurora is present during the day and the night, though during the day it is overwhelmed by the brightness of the sky. As the sun sets, it starts to become visible, being brightest near midnight when the orientation of the Earth’s magnetic field and the solar wind cause it to be strongest. The aurora is seen mostly in a ring centered roughly around the poles, where the solar wind is focused most intensely by the Earth’s magnetic field.

If the Earth had no magnetic field, we’d still have an aurora, but it would be weaker and more flat across the sky: a dull glow seen in every direction. A planet like Jupiter with a stronger magnetic field has a comparably more intense aurora, while Mercury - having neither an atmosphere nor magnetic field - has no aurora at all.

A terrestrial wind passing across the continents creates an unsettled display of turbulence and eddies, which we see in the form of dynamic cloud patterns, vortices, weather, and storms. In much the same way, the solar wind crossing the Earth’s magnetic field makes visible to us the turbulence of space: the vortices and eddies of magnetic fields peel off and pass rapidly overhead.

Even though - like wind - the magnetic fields themselves are invisible to us, we can see it through its tracers: charged particles. As the aurora moves in the sky overhead, the ripples in it are like the wakes and eddies peeling off a boat as at travels up a rough river at night, working at times with, at time against, the current and forcing what’s there out of the way.

2. Timing Is Everything

Now that you know what you’re chasing, when should you expect to actually see your quarry? Sadly there is no easy answer to that question. Here are some notes to consider, as you prepare for the hunt:

• Aurorae are caused by Earth-directed coronal mass ejections. Those ejections often come from solar flares associated with sunspots, or originate from coronal holes on the sun. The sun rotates around into an Earth-facing position roughly every 27 days, meaning that at least on a short term basis there is an element of a 27 day cycle to geoeffective emissions.
  
  
• There is an annual cycle that results in disproportionately high numbers of aurorae in the weeks on either side of the spring and fall equinoxes.
  
  
• There is an 11-year solar cycle (the 'Schwabe cycle') during which the activity of the sun rises and falls. The number of sunspots tends to track this cycle, resulting in prevalent aurorae around the peak of this cycle. Oddly enough, though, coronal holes are most common about three years after the sunspot maximum, resulting in large numbers of aurorae also appearing about three years after the peak of the Schwabe cycle.
  
  
• There are also much longer solar cycles stacked on top of these shorter ones, including cycles with periods of 22 years (the 'Hale cycle'), 87 years (the 'Gleissberg cycle'), 210 years (the 'Suess cycle') and 2,300 years (the 'Hallstatt cycle'). Most of us won’t be around for more than a few of these, though, so there is little sense letting them drive our planning.
  
  
• The weather on Earth is another important factor. If the sky is cloudy, it doesn't matter what's going on above the cloud layer - you won't see it. In much of the arctic, the skies tend to be clearer in late winter and early spring than in fall.
  
  
• Ambient light is another critical issue. In the high arctic, excessive sunlight will overwhelm any aurorae during summer and the surrounding months. The moon is another source of ambient light that must be considered. A partial moon may helpfully illuminate the surrounding countryside, avoiding the “silhouette” effect common in aurora photographs. I usually prefer about a quarter to a half of a moon when I’m including landscape in a photograph and want it to be illuminated. Anything approaching a full moon, however, can make it quite difficult even to see, much less photograph, ordinary aurorae.

Fortunately, the modern auroral photographer can take advantage of a lot of 'real time' information and analysis of so-called 'space weather', freely available online. Resources I recommend include:

• The most informative space weather related information on the net, in my view is www.spaceweather.com.
  
  
• An alternative presentation of similar information is available from the Space Weather Prediction Center.
  
  
• Good short-term auroral predictions for Alaska are available on the University of Alaska website.
  
  
• iPhone and iPad applications 'LightTrac' and 'Darkness,' which provide location-based data regarding sun and moon rise/set.
  
  
• Further information on solar cycles is available on Wikipedia.

3. Location, Location, Location

Photographers in search of exceptional aurora imagery will generally need to travel a significant distance. This is because aurorae form in oval rings that, roughly speaking, circle the magnetic north pole (the 'aurora borealis') and magnetic south pole (the 'aurora australis').  When observed from far away, these rings will appear as a faint glow on the horizon. When viewed from the arctic or antarctic, however, even an ordinary aurora will often appear directly overhead.

Overhead aurorae tend to be more photogenic, clearer and brighter because of reduced atmospheric interference, and will more effectively illuminate the foreground. Auroral displays over snow, for instance, will generally cause the snow to take on the coloration of the aurora. In comparison, when an aurora is low on the horizon, the foreground will often appear as a less-interesting silhouette.

In addition to finding a location remote from the equator, you’ll want to situate yourself far away from city lights, airports, and other sources of light pollution. To give you a quantitative sense of what this means, when photographing around Fairbanks, Alaska (population under 100,000, counting the surrounding boroughs), I prefer to be at least 30 to 40 miles out of town. The farther, the better. Even from 100 miles into the bush, my photos will occasionally still show a faint orange glow on the horizon.
      
Here are a few popular spots:

• Central and Northern Alaska: Relatively easy access from most of the United States, via Fairbanks. Hundreds of miles of beautiful mountain scenery, with year-round road access. The best locations, in my opinion, are along the Dalton Highway north of Coldfoot.
  
  
• Iceland: Astoundingly beautiful landscapes abound, and unfrozen water suitable for reflections is abundant, even in winter. Frequently overcast, but still one of the world’s most wonderful countries to visit. However, travel from most places outside of Europe can be time-consuming, and staying in Iceland can be very costly.
                                                                                                         
• Yellowknife, Canada: Well-situated in the auroral belt, but most photos from Yellowknife seem to feature flat fields of snow with pine forests. 
  
  
• Greenland: At the time of writing Greenland is quite difficult to reach directly from the United States or most other countries, unless you’re a world-class swimmer. There's no road system, but Greenland is a superb place to snowshoe around in the dark, searching for aurorae. Greenland isn't for the faint of heart though - think twice before wandering around in the dark, searching for aurorae in a land filled with polar bears. 
  
  
• Tromsø, Norway: A very long trip from North America, not even counting the time required to find the 'ø' on your computer when booking the flight. This location offers picturesque mountains and water in which auroral reflections regularly appear, but you might struggle to completely exclude the glow of town and city lights from your photographs. 
  
  
• Antarctica: Exotic, and one of few locations where one can photograph the aurora while huddling for warmth with a colony of emperor penguins. Unfortunately, unless you’re a scientist overwintering at a research station, it’s virtually impossible to access the continent when aurora are most prevalent.

As I’m based on the west coast of the United States, northern Alaska has become my preferred location for aurora photography.

4. Gear Up For Battle

When photographers are asked how they managed to achieve a certain result, they will usually point to their own artistic proficiency, not the capability of their tools. 'It’s the photographer, not the camera,' is the common refrain. There are, of course, elements of artistry in aurora photography as well. However, the importance of good quality equipment cannot be overstated. Aurora photography does not require the most expensive kit available; it requires gear that can capture broad views, in low light, in cold weather. You will need:

• A camera body that excels with clean high-ISO operation. There are a number of new bodies in recent years that meet these criteria well, and which have enabled revolutionary advances in the field of aurora photography. Weather-sealing is a definite plus, although not a necessity.
  
  
• A wide, fast lens. On a full frame camera, a focal length of 24mm or less is desirable – but the wider, the better, in my experience. Ideally the lens will be able to shoot sharp pictures with minimal vignetting at a maximum aperture of f 2.8 or less, as you’ll want to keep your exposures short. All else being equal, your exposure will be inversely proportional to the square of your aperture, meaning that a lens at f 2.8 will need four times as long to capture an image as at f 1.4. Currently, my favorite lens for this purpose is Nikon’s AF-S Nikkor 14-24mm f 2.8G ED.
  
  
• A sturdy tripod, and a remote shutter release (or, at a pinch, your camera's self-timer function). Don’t bother leaving home without them. They’re essential for aurora photography. A robust ballhead is also extremely useful.

Gearing up for winter photography, at night, in the arctic, necessitates psychological preparation as well. If you want to get the most out of your journey, you’ll need to be prepared to be awake and working most of the night.

5. Brace Yourself For A Chilly Reception

Aurorae just don’t seem to enjoy the warmth of the tropics or the glow of the midnight sun during summer.  You’ll need to play on their home turf, during the dark months. That means planning to spend hours on end, standing around outside at night, quite possibly in extreme cold, and probably a long way from home.

Clothing: be sure you’re dressed for the occasion. This is not a party you’ll want to attend in a mini-skirt.  For winter aurora photography I’ve settled on a down-filled mountaineering suit (the Mountain Hardwear Absolute Zero), winter boots rated to -40 degrees F (the Sorel Caribou Reserve), multiple pairs of long thermal underwear (Under Armour ColdGear Base 3.0, both top and bottom), and a wind-proof cap (by Mountain Hardwear).

For the hands, you’ll want gloves thick enough to keep you warm, but thin enough to allow you to operate your camera. Personally I prefer to forgo gloves and keep my hands in warm pockets between shots. Most of the time it works fine. If you’re averse to occasional frostbite, try a different approach.

Batteries: The temperatures of the far north take an enormous toll on battery life. My camera batteries last around 1,500 actuations in normal conditions, but in the arctic winter have become exhausted after as few as 25 frames. The conventional cold weather advice is to keep your battery warm by storing it in a jacket pocket while not in use, but that is not an adequate solution under extreme arctic conditions. I recommend bringing multiple batteries and a charger, and rotating the batteries through the charging station when they’re not in use. If your aurora photography will take you far from the nearest well-stocked camera store, consider also bringing backups for any other 'mission critical' elements of your system.

Tripods: Carbon fiber tripods are just wonderful. They’re light, and in cold weather can be carried without chilling your hands as much as metal would. In frigid temperatures, however, both the carbon fiber legs and the adhesive used to connect then to your tripod base can become brittle. Exerting substantial pressure on your tripod, particularly when its legs are buried in deep snow, can easily result in the amputation of a leg. If you’d prefer not to find yourself hundreds of miles from civilization, with only a 'dipod' for support, be particularly cautious when planting your gear in deep snow.

Cameras and lenses: As noted above, weather-sealing is preferable. In part, this is to help prevent condensation from forming inside your equipment, when you move from an exceptionally cold environment (e.g., shooting outside) to a much warmer space (e.g., into a heated car). Particularly for non-weather-sealed equipment, including most medium format cameras and lenses, it is essential that the cold-to-warm transition be made gradually. It only takes one misstep to generate trip-ending amounts of condensation inside your lenses or sensor. To help slow the transition, I transfer my equipment to a camera bag that has also been outside, and only after sealing the bag do I move the bag and its contents into a warmer space. The camera is then allowed to heat up, slowly and safely, within the bag. For even better protection, consider placing your equipment in an airtight enclosure, such as a Ziploc bag, during the thawing process.

Safety gear: If you’re headed to the far north during winter you should, of course, also read up on how to travel safely in cold, icy climates. When travelling in northern Alaska between November and March, I’ll usually bring extra fuel, chemical additives to prevent the fuel from freezing, an oversupply of food (including food that will be palatable when frozen), a cold weather sleeping bag (rated to -25 degrees F), jumper cables and a tow rope with which a vehicle could be rescued after sliding off of an icy road. My tow rope has paid for itself on multiple occasions.