Aurora Borealis Height Determined Using Two Cameras
Brett Smith for redOrbit.com – Your Universe Online
A natural light display seen from high altitude locations in the Northern Hemisphere, the aurora borealis has fascinated people for hundreds, if not thousands, of years and a new photography-based technique has allowed researchers to determine the exact height of the phenomenon.
According to a new report in Annales Geophysicae, a journal of the European Geosciences Union, Japanese researchers used two digital single-lens reflex (SLR) cameras set about five miles apart to create three-dimensional images of the Northern Lights. These images could then be used to calculate the altitude where electrons in the atmosphere generate the light that results in the aurora.
“We had initial success when we projected the digital SLR images at a planetarium and showed that the aurora could be seen in 3D. It was very beautiful, and I became confident that it should be possible to calculate the emission altitude using these images,” said Ryuho Kataoka, from the National Institute of Polar Research in Tokyo, Japan.
The distance between our eyes allows us to perceive the world around us in three dimensions. When we look at an object, the images captured by the left and right eyes are slightly different. However, our brain combines these images to create the perception of depth. Because the distance between our eyes is only a couple of inches, this depth perception works for objects that are relatively close.
Since the aurora occurs between about 56 and 250 miles above the ground, a much larger separation was necessary to generate the 3D image. Therefore, the Japanese research team used two cameras, replicating the left and right eyes, separated by about five miles in an area of Alaska. Using fisheye lenses and GPS units, the two cameras captured two concurrent images that were later combined to create a 3D photograph of the phenomenon and measure the emission altitude.
“Using the parallax of the left-eye and the right-eye images, we can calculate the distance to the aurora using a [triangulation] method that is similar to the way the human brain comprehends the distance to an object,” explains Kataoka. Parallax is the disparity in the perceptible position of an object when seen at different angles.
While scientists have created altitude maps of the aurora before, this is the first time the emission height of the Northern Lights has been determined by using digital SLR cameras. The research team noted that the altitude maps they generated matched with previous observations.
Kataoka noted that the technique is relatively inexpensive and allows scientists to determine the altitude of various elements in the aurora. Additionally, the technique opens up the possibility for citizen scientists to get involved with researching the polar phenomenon.
“Commercially available GPS units for digital SLR cameras have become popular and relatively inexpensive, and it is easy and very useful for photographers to record the accurate time and position in photographic files. I am thinking of developing a website with a submission system to collect many interesting photographs from night-sky photographers over the world via the internet,” Kataoka said.