The Summer Night Sky
Now that the nights are shorter and real darkness doesn’t return until the autumn, there won’t be any Northern Lights to see, and the milky way will have faded. Many astronomers pack their telescopes away until later in the year, but there are still plenty of things to look at.
One of the summer highlights is the appearance of noctilucent clouds. They look like bands of electric blue or silver clouds on the northern horizon, except we don’t see clouds at night! These clouds are at the very highest reaches of the atmosphere and we are at the perfect latitude to view them. They are caused by sunlight reflecting off tiny ice crystals formed around miniscule particles. There is a correlation between increased atmospheric pollution and their appearance, but this is still being investigated by scientists.
The planets Mars, Saturn and Jupiter are prominent in the sky in June. Mars is very bright in the southern sky, and Saturn is also quite bright, to the east of Mars. Jupiter is the brightest ‘star’ in the sky at the moment. All the planets follow a similar path to the moon, rising in the east and setting in the west.
Come the autumn, we will be holding a number of stargazing evenings, many of them at Ingram at the valley café. Full details will be published nearer the time, but they will all be free to members.
The Aurora Borealis, or Northern Lights, is a natural phenomenon caused by particles thrown out by the sun interacting with molecules and atoms in the earth’s atmosphere and releasing energy in the form of visible light. The science behind it is well understood but a visible aurora in Northumberland is unpredictable for many reasons.
Where to see it
In the north. Simple as that. You can go anywhere with a clear view to the northern horizon. If you are inland, the higher you can get the better. The coast is the usual destination for most people, but it’s not necessary. Car headlights, light pollution, camera flashes and crowds at some locations can make it a less than edifying experience. There are literally hundreds of places around the county that are light pollution free and you can be alone to be able to experience the full majesty of a strong display, but it takes commitment and perseverance. Don’t be afraid of the dark. Darkness is your friend. There are no ghosties, lions, dinosaurs, bears or werewolves in Northumberland. There is only a slim chance of meeting an axe murderer and he will probably be too busy watching the aurora to bother with you. But if you are going to go yomping up a remote hillside, tell someone where you are! The best places tend to be out of range of any mobile signal, so if you do get attacked by wolves we will know where to come and retrieve your remains.
How to see it
Sometimes the aurora will be visible only by using a camera, and other times it will look just like a grey milky glow on the horizon. If it is a strong display, however, you will see shafts and curtains of light reaching into the sky and moving laterally. But you must give it time. The human eye can see very well in darkness, but you have to allow at least 20 minutes for full adaptation to night vision. The eye reaches its maximum sensitivity after about 40 minutes. The downside to this is that we only see in black and white in dark conditions, as the light gathering receptors in the eye take over from the colour sensitive ones. However, in a bright display, the colours will become visible, so persevere. A flash of car headlights will destroy your hard earned night vision, as will a torch, the flame from a nearby cigarette lighter, the internal lights of cars, camera flashes, iPhone screens and so on.
Photographing the aurora
To get a meaningful result, you will need a DSLR and a tripod. A fast wide angle lens is preferable, where you can set the aperture to f2.8 or wider. There are no definitive settings, it depends on the brightness of the display and the amount of ambient light and pollution. Always shoot in RAW format and turn off the in camera noise reduction in the camera settings. Focussing is difficult at night and auto focus will not work, so you must be able to set your lens focus to infinity using manual control. Practise in daylight until you are confident that you have it right, then check each image to make sure the focus is spot on. If your camera has live view, point it at a bright star and zoom in as you adjust the focus.
As for settings, a good starting point is to set the aperture to its maximum, i.e. f2.8. Set the ISO to 1600 and the shutter speed to 15 seconds and see what you get. You can change the shutter speed up to 30 seconds on most DSLR’s. Don’t be frightened to bump up the ISO to 3200 or even higher if you have a full frame camera. However, if the display is giving moving curtains of light, the shorter you can make the shutter speed, the better you will capture it, so go with a higher ISO and shorter shutter speed. If you don’t have a cable release (less than a fiver on eBay), use the self-timer to avoid camera movement when activating the shutter.
A certain amount of post processing will be needed in most cases, as by shooting in manual and turning off noise reduction you will invariably get some noise showing on the image. There are lots of tutorials on YouTube, but some Photoshop skills are desirable. Don’t go mad with the saturation tools though! Aurora observers know what the reality is and can easily tell when the image has been over-manipulated, tempting as it may be to make it look more colourful.
Predicting the aurora
There are lots of phone apps available – I personally don’t use them. A good website is www.spaceweather.com, where you will get up to the minute details of solar activity. A good but general rule of thumb is that 2 – 3 days after a large solar event, the chances of seeing an observable aurora are greatly increased. Pay particular attention to the Bz index. The smaller the number the better the chance of seeing something, and it must be pointing south. Don’t pay too much attention to the much talked about Kp index. It is, at best, a very rough guide to geomagnetic conditions as a global average over the previous couple of hours. I’ve photographed bright aurora when the Kp index was showing 3 and seen nothing when it was at 6, so don’t get hung up on it.
The bottom line is that you won’t see the northern lights if you just go somewhere and look, expecting to see a sky dancing with bright colours, then leave in a strop when it isn’t obvious. You need to persevere, get your night vision and wait it out for a couple of hours in a dark place. Stick it out. Many people can’t do that due to work and family commitments, but for strong displays, it’s well worth a long night in the cold and a subsequent day of tiredness. Most times you will be unsuccessful, but when you do hit it right, it’s breath-taking.