After having seen northern lights out of a sudden on a hiking trip to Rättvik in Dalarna, nature was gracious and revealed them again last night. As I had seen that the aurora forecast was promising even for the Stockholm area, I kept taking long exposure pictures out of the window of my room. And what did I see? Clouds. A lot of clouds, looking exactly like the ones that almost prevented us from seeing the super blood moon two weeks ago. By repeatedly opening the window, I had cooled down the room to 10°C and managed to take some nice cloud pictures. I started feeling really displeased about the Swedish weather.
But than out of a sudden, I looked at the photo on my camera, expecting another piece of my cloud collection, and saw the most intense picture of an aurora I have taken so far. In fact one could see the northern lights with the eye just around the corner. We were of course excited and started thinking about a place where we could go to see the aurora more clearly. The aim was to go to a place where there was no city in the north, because cities emit a lot of light during night, that can cover the northern lights.
We decided to go to Tullingesjön, a lake between Tumba and Tullinge in the south-east of Stockholm with a group of seven people. Having arrived there, the view at the northern lights was amazing. Between the clouds huge areas of green light appeared and one could even watch them change shape.
Unfortunately clouds gathered again and blocked our view at the sky. Anyway, the pictures I had taken so far were better than the ones from Rättvik because the clouds make the pictures more interesting and because I figured out how to get the pictures in the box more effectively.
How Does an Aurora Borealis Occur?
A northern light or scientifically an aurora borealis, is a natural light display caused by charged particles that enter the magnetosphere of our planet. The particles originate at the Sun where they are sent to Earth in solar winds. The magnetic field of our planet protects us from these winds by deflecting the charges as a result of the Lorentz force. Close to the poles the particles can sometimes enter the atmosphere where they hit several molecules such as oxygen and nitrogen. These atmospheric components are excited and emit light as a result. Depending on the composition of the atmosphere, the light can be red or green. As our eye can most easily see the green color, this is the most common one.
Update: Read here in detail about the physics of northern lights.
How to Find Out When Northern Lights are Visible?
There are websites like Aurora Forecast that publish real-time data from spacecrafts that measure the activity of solar winds in the orbit. By means of this data a value can be calculated that reveals where northern lights are visible. The higher the value is, the further south they can be seen. In order to have a good chance to see them in Stockholm, the value should be at least 6 kp. During this night it went up to 9 kp.
There is also an app for Android called Northern Eye App that provides the data on you smartphone. Additionally it has the possibility to set an alarm in case the kp-value reaches a certain threshold. Do you use a different app? Please let me know in the comments below! Update: Kevin suggested Aurora Forecast for iOS.
How to Take Pictures of Northern Lights?
As I already had two chances to take pictures of an aurora and received many advises from others, I found some settings on my camera that capture the moment quite well and I want to share them with you. Even though we managed to take pictures even with a smartphone, to get the best results you should have a system camera and a tripod. In my case it was a “dipod” in form of a bike, but that worked fine as well!
The most difficult part is to set a proper focus point. Because there is not a lot of light, the camera’s autofocus will fail, if you point it at the northern lights. If the moon is visible, try to focus there instead, as it has a similar distance, and then set the focus to manual (MF) in order to lock it. If you cannot focus on the moon, try different manual settings until you like the result.
Your camera has a mode M, where you can set every setting on your own. In fact, there are three important settings that you can influence: the aperture, the exposure time and the luminous sensitivity (ISO value).
- The aperture defines, just like the pupil of your eye, how much light will shine in the camera. As we want to have as much light as possible, we have to open the aperture. The numbers indicating the aperture-opening are in reciprocal quantities, thus small values correspond to a large aperture. The minimum aperture value depends on your objective, but try to set it as low as possible (usually 2.8 or 3.5).
- The exposure time defines how long the light will shine on the sensor. The longer the exposure time is, the more light you can capture. But as the northern lights, the clouds and even the stars are moving, the exposure time will strongly influence the result. I took most of the pictures with 20 sec exposure time. This has caused the clouds to be blurry, revealing their movement. Even the stars have moved above a small angle. Shorter exposure times would result in sharper but also darker pictures.
- The third critical value is the luminous sensitivity or the ISO value. It influences how strong the sensor of your camera will react to the incoming light. A high ISO value produces luminous pictures, but you have to buy this advantage with a drawback. The more sensitive your sensor is the more noise will appear on the picture making it appear granular and in wrong colours. Even though your camera will probably be able to set very high ISO values you should set it to a maximum of ISO-800, better ISO-400 as for the pictures shown here. Especially in combination with a long exposure time, noise can disturb your picture quite easily.
Finally, you should rely on the picture you take with your camera and not try to alter it too much with a graphics editor. This will only make it appear unnatural. In my pictures I only slightly edited the illumination and the local brightness in order to dim out lights from the streets.
This said, I hope you give it a try during the next aurora that is visible near to you. Do you have any other suggestions or experiences? Please share them with everybody in the comments below!
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