Predicting and photographing the aurora at mid latitude
Photographing the aurora at mid-latitudes defined as between 50° and 60° magnetic latitude (e.g. Scotland, Northern England, Ireland, Northern USA, New Zealand South Island, Tasmania) can be challenging. Visible displays are only present at times of significantly heightened activity but may be present more frequently than you might imagine. Long exposure photographs may bring out displays not visible to the naked eye. Here are some tips.
Factors influencing likelihood of auroral sightings
• Solar cycle – peaks every 11 years. Cycle 24 peaked in 2014
• Statistically highest activity around March and September equinoxes
• Summer months may not get sufficiently dark
• Strongest activity around midnight (ignoring daylight saving correction)
• Time of moon cycle – a full moon can obliterate weak auroral activity
• Cloud cover
• Higher latitudes increase you chance of sightings but you are unlikely to get a significant benefit from a couple of hours driving northwards.
• Avoiding light pollution. Keep the northern horizon dark. Long exposure photography can amplify light pollution quite considerably, even from small villages.
• Flat terrain on the northern horizon will allow weaker displays to be seen
The majority of auroral displays are a result of impact of coronal mass ejections (CME) or a coronal hole high speed streams (CHHSS). Activity is more likely near the peak of the solar cycle and directly relates to sunspot number.
• CME’s are released from some but not all solar flares and originate from sunspots. Higher complexity sunspots yield more CMEs which in turn are more likely to hit earth if the sunspot is earth facing. Larger solar flares e.g. M and X-class typically generate larger CME’s. A CME will typically take 3 days to reach earth but varies depending on speed.
• CHHSS originate from coronal holes on the sun. Usually their effects are milder, but can still give nice displays
• Impending impact is picked up by ACE satellite (~1hr before impact with earth). Look for increase in proton density and solar wind which is sudden with CMEs and more gradual with CHHSS. ACE also displays information on the polarity of the incoming solar wind (Bz). If this is southward (negative value) auroral activity is much more likely.
• Impact with earth is picked up on magnetometers. Find one local to you (e.g. aurorawatch in UK). Kp values are generated using magnetometer data and will give a global value of activity (0-9). The required Kp depends on your latitude and is only a rough guide.
• Ovation and POES aurora maps interpret real time data and will predict the extent of auroral activity making life a bit easier.
• Social media – dedicated pages e.g. facebook are invaluable
• Newspapers – if you wait to see the photos here you may be too late
• A tripod is virtually essential as your camera must be still
• Typical starting settings
• Manual mode if available
• Focal length – wideangle often gives the best results
• Aperture – go for widest available e.g. f3.5 to let the maximum light in. This will allow shorter exposure times/lower ISO
• Shutter speed – 30 seconds (any longer and stars start to trail). Reduce if you can in stronger displays.
• ISO 1600 but reduce if you can to improve image quality.
• Focus – manual and set to infinity (likely to need fine tuning). Alternatively focus on bright object in distance e.g. moon using AF then switch to manual focus. Tape the lens to avoid accidental movements.
• Shoot in RAW if available – allows white balance and exposure correction afterwards
Other useful equipment
• Torch. A red filter will preserve night vision. Can also be useful for light painting foreground (LED lights often give less pleasing results when light painting)
• Warm clothes including gloves and sturdy footwear.
• A smartphone for following real time auroral activity provided you have not lost reception!
• Remote shutter release for steadier shots and exposures longer than 30 seconds (using bulb mode). This will also allow easy capture of multiple consecutive images which can later be merged to a star trail or time lapse footage.
• Food and drink – especially if you are out for the night!
Other general tips
• Sightings are most common above northern horizon unless you are lucky and the aurora is powerful when it may even be above you
• Consider the foreground to give your finished article more impact
• The moon can make a nice feature, particularly if less than half illuminated. If close to the horizon it can give nice foreground lighting
• Don’t give up and good luck!
Predicting And Photographing The Aurora - printable guide (click to download).