[On the night of September 12/morning of September 13, 2014) there was a strong geomagnetic storm that produced a wonderful, albeit short-lived, Aurora Borealis for much of northeastern North America. This blog post is intended to provide you with background information on the natural phenomenon (and since I’m just a fish geek, it will only cover the basics) and how to see/photograph it.]
“Where did you see them?” “What are they?” “How can I see them from where I live?” These are probably the three most common questions I see relative to the Northern Lights (or Southern Lights if you live in the Southern Hemisphere), and they’re the same questions I had before I saw my first light show. I will attempt to quench your thirst for these answers here in the following paragraphs.
Let’s first begin with what the Northern Lights are, and to understand this we need to look beyond our home planet and to the star that keeps life on Earth living. Periodically, the sun lets loose a massive explosion called a Coronal Mass Ejection (CME). Massive, in fact, is an understatement. Think close to a billion atomic bombs detonating at once! Flung into space are solar winds composed of charged particles (primarily electrons). As the solar winds approaches Earth, it is suddenly deflected by the magnetosphere, which essentially acts as a security guard and shields our planet from potential damage caused by solar winds. However, some of these particles and their subsequent energy is stored in the magnetosphere. As the energy builds, the magnetosphere becomes destabilized and in order to regain stability, there is a sudden release of energy (usually in the form of accelerating electrons), which travels down the magnetic field lines around Earth and into our atmosphere.
When these electrons hit the atmosphere, they begin exciting molecules (moving electrons within the nucleus to higher energy orbits) and, as they stabilize and return to ground state, the energy produced during all that excitement is released as colored light (photons). Different colors signify different molecules being energized in different parts of the atmosphere.
- Blue – nitrogen, up to 60 mi/100 km in altitude
- Purple/violet – nitrogen, above 60 mi/100 km in altitude
- Green – oxygen, up to 150 mi/240 km in altitude
- Red – oxygen, above 150 miles in altitude
Each CME is assessed by orbiting satellites and classed into five categories as A-, B-, C-, M-, and X-class flares. The designations reflect the amount of X-rays coming into contact with the satellites near Earth. A log scale of 1-9 is used within each class such that an M4 flare is twice as powerful as an M3. For purposes of seeing the Northern Lights, we are really only concerned with M- and X-class flares. (If you’re bored already or haven’t yet channeled your inner science nerd, you may consider skipping down a few paragraphs).
http://solarscience.msfc.nasa.gov/images/combo.gif (Coronal mass ejection GIF, NASA Solar Physics Marshall Space Flight Center)
Occasionally – actually it’s only happened once – explosions occur that defy this current classification scheme. In 1859, the largest flare on record occurred that scientists today would classify as a Z-class flare. This event, known as the Carrington Event, allowed people in the Caribbean to see the Northern Lights. Telegraphs malfunctioned causing some to spark and throw fire. Operators could unplug their telegraphs and continue sending messages 60-90 seconds later as the batteries continued to hold a charge. Gold miners were woken by the glow of the lights; thinking it was the wee hours of the morning, they began making breakfast and preparing for the day’s work. The National Academy of Sciences published a report in 2008 discussing the ramifications of something like the Carrington Event occurring today. They estimated the global cost of a similarly sized geomagnetic storm to be upwards of $2,000,000,000,000 ($2 trillion!).
But I digress. Predicting these events is futile; unless you’re Neal Degrasse Tyson and even then I still wouldn’t bet $20 that he would predict accurately. You can, however, manage your expectations. Every 11 years the Sun undergoes a new solar cycle, which means that every 11 years there are varying changes to the Sun’s radiation, polarity, sunspot visibility, and flare occurrence (among other things). We are currently in the 24th Solar Cycle, which technically began in 2008, but little activity was noted until 2010. Still, Cycle #24 is the weakest since record keeping began in the mid 1700s. It is around these changing solar cycles that the probability of seeing the Northern Lights increases substantially. Fortunately, there are services offered on the great, magical Interweb that make Aurora spotting almost effortless. I, personally, use Aurora Alerts by Soft Serve News. This service can provide you with notifications of possible Aurora activity via their Facebook page, Twitter account, or through their customizable text or email service. I also have an App for my iPhone and know other photographers use various apps, consult Aurora Alerts, and view data provided by NASA. What these various sources will communicate is numbers in the Kp Index. I won’t bore you like I have above, but it is sufficient to say that the Kp Index is a scale that measures the strength of geomagnetic activity. The higher the Kp Index, the more powerful the “storm” is. It’s that simple.
Sort of. Recall that the Carrington Event was so powerful people in the Caribbean could see it. This means the Kp value must have been enormous. Yet, when people in the Yukon can see the Aurora often people in the Caribbean cannot. That’s because the Kp Index must be much higher for someone in the Caribbean than in the Great White North. Indeed, your ability to see the Aurora will vary depending on where you live. Check out the photo below. It’s a map of North America showing guidelines for what threshold is needed to see the Northern Lights in your location. Prince Edward Island (where I’m currently typing this) sits between the Kp 5 and 7 lines on the east coast of Canada. So, the Kp needs to be around these numbers in order for us to see them. In the Chicago area, which is where I’m originally from, the Kp needs to be around 7 or higher to see them. If you are located in Iqaluit, Nunavut you need something around Kp 3 or maybe even less… but chances are those folks aren’t reading this because seeing the Northern Lights is such a common occurrence they probably aren’t curious about it!
OK, so now you know what the Northern Lights are and how we measure them. Seeing them is the next step. As I mentioned above, viewing the Northern Lights will depend greatly on where you are located. If an event occurs and, according to the Kp Index, you should be able to see it, then the rest is easy. Go to a place with little light pollution (read: go someplace rural) and look north. You also need to remember to try and not look at bright light sources too much; this will ruin your night vision. And if the moon is set to rise sometime during the night, try to get out and view the Northern Lights before moonrise. The moon will wash out the sky and you won’t be able to see them, which is what happened to many people on September 12/13 when they set out to view the Aurora after 9:30 or so when the moon rose.
Photographing the Northern Lights
Capturing the Northern Lights on film (memory card?) is relatively simple if you follow a few guidelines.
- Tripod – This is an essential piece of gear. I suppose if you had a dead tree stump or a pile of rocks that would work, too. You will be using long shutter speeds so having a stable base is critical to getting something that doesn’t look like a blurry mess.
- Go wide – Use a lens that has a wide field of view. Even if you only own a kit lens, usually these range in focal length from 18-55 mm. In that case, use 18 mm.
- Open up – Night photography relies on collecting sufficient light on the sensor to see objects (or in this case, colored light). You need to open your aperture as much as possible to facilitate this happening.
- Go high – Increasing your ISO will also help your camera collect light. This will take some experimentation, but I would start around 800-1,000 ISO. However, this is hugely camera dependent as 1,000 ISO is the absolute maximum on some older cameras and will yield awful “noise” in images. On the other hand, 1,000 ISO may be child’s play to something like a Nikon D800 or Canon 5D Mark III and thus you can increase it even more.
- Go long, but not too long – The #1 mistake I see people make that try to take pictures at night is they use a shutter speed that is too long and produces trailing stars, which is a distraction and a flaw. Sorry, but I hate looking at night images that have trailing stars (unless it’s purposeful and that’s evident). Follow this rule and you’ll be fine: 500/focal length = shutter speed. This is termed the “500 Rule” and is a simple calculation that lets you determine what the maximum shutter speed you can use without creating trailing stars. For example, if you’re using a 20 mm lens you would take 600 divided by 20 and get an exposure of 25 seconds. If you use a crop/APS-C sensor, you need to convert your focal length to full frame terms. For example, if I’m using a Nikon D7000 (crop sensor) with 11 mm focal length and I know Nikon’s crop is 1.5X, then the equation becomes 500/16.5 which gives me a 30 second exposure.
- One caveat is that the longer your exposure, the less movement in the Aurora you’ll capture on camera. If you’re at high latitudes (like Alaska, Yukon, Iceland) then it’s wise to keep your shutter speed short so you can capture some of the beautiful shapes the Aurora takes in these parts of the world. For everyone else at lower latitudes, you should be OK with around a 30 second exposure, since the Northern Lights generally don’t behave like they do in these other areas.
- Composition is still key! If you’d like to step your game up a bit, you need to challenge yourself to not only capture the Northern Lights, but do so in a way that is compositionally pleasing. Look for leading lines! Use leading lines to your advantage by guiding the viewer into the image. I spend a lot of my time looking for places that have features pointing north such as cliffs or land extensions. Use frames! Try to find something that might frame the Northern Lights in an interesting way, even if it’s very subtle. For example, using cliffs or hillsides to focus the viewer’s eyes toward the Northern Lights is effective. Incorporate other elements! Don’t make the image busy, but other landscape features will be visually more appealing. Strive to first create a good landscape image, and then focus your attention on the Northern Lights. Reflections! The Northern Lights reflecting on water or ice adds just a little something extra special.
I won’t go into processing details here, as that requires a whole other post, but generally speaking these are easy… unless you’re Marc Adamus focus stacking ice formations and towering mountain peaks “Green Vision” by Marc Adamus. In which case, things can get a little more complicated! [I hope that those reading this are familiar with Marc’s work. If you’re not, you need to be. The image I’ve linked to gives you an idea of what a compositionally excellent Northern Lights image should look like.] If you have any questions or comments, leave them in the comments box on this page! Or alternatively, you can drop me an email at firstname.lastname@example.org.