Auroras appear to the naked eye as a very faint, white glow in the night sky to the magnetic north. Many auroras are totally invisible to the naked eye or can only be seen by looking at them indirectly, i.e. out of the corner of your eye. It is extremely rare to see them in colour with the naked eye.
You need a digital SLR camera and a tripod. Take a test photograph of the sky to the north, using the settings I suggest below. Then view the image on the telly on the back of the camera and look for green. If you see a strong green arc then there is an aurora present.
Wait until it is dark. Generally the earliest time you can capture the aurora is mid-way between the nautical twilight time and the astronomical twilight time for your location.
The closest place to where you are staying that has a clear view of the horizon to the north and is without light pollution. Ideally, a view to the north over the sea or a loch is best.
Auroras can be cutting through the sunset and still there at sunrise but the best time is in the darkest part of the night, i.e. mid-way between the sunset time and sunrise time for your location. On Skye this is around midnight on the winter clocks or around 1:30am on British Summer Time. This does not mean that you should stay inside until midnight, as many auroras only last for less than an hour and you may miss the activity. What it means is that when an aurora settles in for the night, the photographs will be better in the middle of the night, so don't go too bed early thinking you've had the best of it.
You cannot see auroras on Skye in June and July because it is too light at night. The best times of year are late September to early April.
We can generally only tell a maximum of 4 days in advance if there is a likelihood of any geomagnetic activity. There are three factors that are essential to getting an aurora: geomagnetic activity, clear sky and darkness. It is very difficult to achieve all three of these things at the same time, particularly at certain times of year, e.g. in June/July it never gets dark at night.
In the summer months, the window of darkness is very short, so the chances of meeting all three criteria is much lower. In winter, the period of darkness is much longer, so the chance of getting auroras is much higher.
At all times of year, cloud is the main limiting factor that prevents us from seeing the aurora.
I always post photos on the Glendale Skye Auroras Facebook Page if I am getting the aurora on camera or by eye. You should make sure that the 'sort' option on your facebook feed is set to 'most recent', rather than 'top stories', if you want to be sure of seeing the latest updates. If you have clear sky it is always worth taking test photos at regular intervals to see whether you get any green. You can also subscribe to my text alert service.
You can subscribe to my Aurora Text Alert Service to receive text alerts directly to your mobile phone by following the twitter feed as follows :
You don't have to tweet or use twitter in any way. This is just a free way to be able to send you a text message directly to your mobile.
n.b. If you do not see the 'turn on mobile notifications' option, do the following:
If I am posting photographs of the aurora in Glendale then it can be photographed anywhere in the UK but with a caveat that for every two degrees of latitude further South you will need to increase the exposure on your camera by 1 stop relative to what I am using. My latitude is 57.5°N. If I am photographing the aurora at F4 ISO800 30s then at Bamburgh in NE England (55.6°N) you would need to use exposures of F2.8 ISO800 30s or F4 ISO1600 30s or F4 ISO800 60s. The aurora will also subtend a lower angle in the sky relative to what you see in my photos, the further south you are.
A magnetometer is a device that measures deviations in the Earth's magnetic field, which might indicate that there is an aurora in progress. The greater the disturbance, the better the aurora is likely to be. Magnetometers are very slow to react to geomagnetic disturbance and the peak of auroral intensity generally occurs at least 15 minutes and, as much as, an hour before the magnetometers measure their peak disturbance. Norwegian magnetometers generally react faster to visible auroras than UK-based ones. In many cases, UK magnetometers fail to detect activity or react a couple of hours after the light show started. For this reason, I prefer to take regular test photos of the night sky, rather than monitoring magnetometer plots.
K is a measure of how much geomagnetic disturbance there is at a particular location on the globe. Kp is an average of K readings from across the planet. The higher the K number, the better the aurora. Putting it another way, the higher the K number of the aurora was, the more gutted you will be that you missed it.
G1, G2 and G3 are alternative names for Kp 5, Kp 6 and Kp 7 respectively.
Kp 4 can produce very good auroras on Skye that are excellent on camera and also visible by eye in faint white. Kp 7 and higher can produce auroras that are in vivid colour to the eye.
A Coronal Mass Ejection is a plasma blob that the sun periodically emits from active sun-spots. If the blob hits the earth's atmosphere it can cause some of the best auroras. It is rare to get a direct hit. Think of it like the sun sneezing and the chance of some of the snot hitting an 8000 mile wide rock that is 93 million miles away.
Using the above analogy, if a CME is a sneeze then a Coronal Hole High Speed Stream is runny nose. It is a constant leak of plasma from a hole in the sun's magnetic field that sprays out into space. When one of the coronal holes is facing towards the earth, we can have a gentle dribble of snot hitting our atmosphere and causing auroras that are less intense than those caused by CMEs but continue for days rather than hours.
Bz and Bt are measures of the strength and direction of the interplanetary magnetic field between Earth and Sun. Using a simple analogy, think of the aurora as being like the light from a rechargeable torch. When the Bz is south (negative), the torch is charging. When it is north (positive) the lights (aurora) come on. How long the light lasts, and how bright the display, depends on how long it was on charge and how strong the charge was.
These are the settings I use for my test photos, with some recommendations alongside:
If the aurora is exceptionally bright in your test photo, always reduce the ISO in preference to the shutter speed, as this will reduce camera noise or graininess. Don't even think about reducing the shutter speed until you have reached an ISO level at which your camera produces acceptable amounts of noise. Never close up the aperture, you should always keep to the lowest F-number your lense can support.
Always make sure that there is some landscape, building or scenery in your aurora photo to give some scale or perspective. Never just shoot at the sky, unless you are lucky enough to experience a corona (overhead aurora).
Never make any adjustments in your photo-editing software that change the colours from those that your camera originally captured. This results in photos that look 'cartoonish' and totally unnatural.
Practice taking night shots on clear nights when there is no aurora, so that you know what you are doing when the aurora shows. The thing most people have problems with is the focus. Until you can take a nice, sharp, night-time, landscape photo that looks like daylight but with stars, you will not be able to capture an aurora.
Go to Daily Rise/set and Twilight times for the British Isles and click the map pin that is closest to your location. This link has all the essential times that you need for aurora-watching.
No, it is not bright enough. When you have seen 'video' footage of auroras this is generally done using time-lapse photography, where many hundreds of long-exposure, still images are joined together to create a short piece of video.
No. When the sun is setting, refraction splits the light into the colours of the rainbow: red, orange, yellow, green, blue, indigo, violet. Arcs of each colour appear above the horizon where the sun is going down, the typical colours of a beautiful sunset. There is often a wide, green band around the sunset. Blue, indigo and violet are not strong enough to show until the sun is well below the horizon.
If you get green on camera before the astronomical twilight time for your location, it could just be sunlight, so wait until after astronomical twilight time and then take another photo to confirm that green is still there.
Between nautical and astronomical twilight times, it is not unusual for your test photo to capture a sky that is largely purple or navy blue. This is not an aurora, it is the refraction of the sunlight causing blues, indigos and violets of the colour spectrum to become visible.
No. Orangey or yellowish glows in the sky, particularly when reflected on clouds or visible in colour as orange/yellow by eye, are caused by light pollution from human settlements.