Tuesday, 22 November 2016

The BGS Aurora Camera (AuroraCam) Blogspot...by Ciaran Beggan

Background
In early 2016, the Geomagnetism team decided to install an experimental camera at the Eskdalemuir observatory to see if we could observe the Aurora Borealis during times of heightened geomagnetic activity. The aurora are caused by large electrical currents flowing in the ionosphere around 110km above our heads. These current systems are normally found in an oval around the magnetic pole at high latitudes (such as over Iceland), but during geomagnetic storms the oval expands southwards and can move to lower latitudes.

When it does, the magnetic field recorded at our observatories starts to vary rapidly – first at the station furthest north in Lerwick (Shetland Islands), then in Eskdalemuir (the Scottish Borders) and, if the storm is large enough, in Hartland (Devon).  During these stormy periods, the aurora may become visible – though it’s not always guaranteed. The Geomagnetism team do try to issue alerts if we think the aurora may be visible in the next day or two.
Raspberry Pi with camera in its IP68 box. The lid
with a Perspex dome is to the left.

Hardware
We decided to see if we could capture images of the aurora ourselves, by using a camera automatically triggered from magnetic field variations at an observatory. We’ve been working with Raspberry Pi computers for our School magnetometer project over the past few years so we are familiar with them. As you can now buy a cheap five mega-pixel camera for the Pi, it seemed a good system to experiment with. There is plenty of advice on the Internet about how to build a time-lapse camera like this.

Software
Once the hardware had been built, the next step was to write the software to drive it. As the Raspberry Pi comes with the Python language, it seemed the obvious one to use.

We wrote a small piece of code to (a) check if it is dark and (b) to check if the geomagnetic activity measured at our observatories is high (above some particular threshold). If these conditions are met, the camera is triggered. It takes a six -second exposure. A timestamp is placed onto the image and a note is made into a log file and then the system goes to sleep for five minutes. The camera continues to take images every five minutes until the geomagnetic activity declines or the sun rises.

Installation
The camera was installed in June 2016.  The first task was to lay the cables for power and communications from the ground floor office to the roof. This involved passing a cable through two floors, a window and up to the balcony where we wanted to mount the camera. Once the wire was laid, the camera was mounted on some unused scaffolding.
 
From L-R: Tim Taylor mounting the camera on the roof, the camera is angled to point north and just captures the top of the
horizon in the image to the right; Camera pointing north on a typical (i.e. cloudy) day in Eskdalemuir.
Aurora pictures?
There have only been a few large storms since we set up the camera in June 2016. However, the camera has been triggered by a few periods of higher activity but usually it is raining or cloudy. The best image we have was captured at 4:34am on 28th September 2016. It shows stars and a very faint aurora on the horizon. The photo has been processed to increase the gain and the colours have been auto-corrected using an image processing package.
 
Image captured by the Eskdalemuir AuroraCam on 28/09/16 at 03:34 UT.
Future plans
We plan to add images of the aurora to our alert pages the following day once they have been processed. It will be interesting to see if this relatively cheap setup will survive the cold and stormy winter months in Scotland.

For more information on the Aurora Cam then visit the website here.

By Ciaran Beggan & Tim Taylor, with thanks to Ted Harris and Tony Swan.

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