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You Can Measure the Height of Northern Lights Using Digital SLRs

Aurora by DLSR

The all-sky images of aurora captured simultaneously by two digital single –lens reflex (SLR) cameras equipped with fisheye lenses and GPS units. The nuances between these two images make it possible for researchers to fabricate 3D images of aurora and hence determine the altitude where electrons in the atmosphere emit the light that produces aurora. *Image source: Kataoka et al., 2013.

Scientific research rarely start from outreach projects. Yet, Ryuho Kataoka from the National Institute of Polar Research in Tokyo, Japan, came up with a novel approach to measure the height of aurora after working on a 3D movie for a planetarium. Using two digital single-lens reflex (SLR) cameras set 8 km apart from each other, Kataoka and coworkers were able to capture 3D images of Northern Lights and determine the altitude where electrons in the atmosphere emit the light that produce aurora. The new findings were published in Annales Geophysicae, a journal of the European Geosciences Union (EGU).

 “We had our initial success when we projected the digital SLR images at a planetarium and demonstrated that the aurora can be seen three-dimensionally,” recalls Kataoka, who also works at the Graduate University for Advanced Studies (Sokendai) in Hayama, Japan. “The 3D aurora was so beautiful and I became confident that it should be possible to use these images to calculate the emission altitude.” He teamed up with other Japanese and American scientists to do testify his idea.

The separation distance between human eyes is what allows us to see things in 3D. When we are looking at an object, the images captured by the left and right eyes are slightly different and when they are combined, our brain perceive the depth. However, due to the small distance between our eyes – around 5 cm – this only works for objects that are relatively close.

Aurora extend between approximately 90 and 400km in altitude, hence, a much larger separation distance is required to see them in 3D. The researchers utilized two cameras – separated by 8 km across the Chatanika area in Alsaka – to mimic the left and right eyes. The two digital SLRS were equipped with fisheye lenses and GPS modules and successfully captured two simultaneous all-sky images that the researchers combined to create a 3D image of the aurora and measure the emission altitude.

 “Using the parallax of the left-eye and right-eye images, we can calculate the distance to the aurora through a triangulation method similar to the way our brain comprehends the distance to an object,” Kataoka explains. “Parallax is the difference in the apparent position of an object when it’s observed from at different angles.”

Researchers have obtained altitude maps of aurora in previous studies. They are useful because they offer insights about the energy of the electrons that generate the lights. Yet, this is the first time the emission height of Northern Lights has been measured using photographs captured by digital SLR cameras. As the authors note in the new Annales Geophysicae paper, the altitude maps created using this new approach are consistent with previous results.

This technology is low cost and allows researchers to determine the altitude of small-scale aurora features. In addition, it also opens up the door for citizen scientists to get involved with auroral study.

 “GPS units for digital SLRs are now commercially available and popular with relatively low price, and it’s easy and useful for photographers to record the accurate time and position in photographic files. I’m considering of developing a website with a submission system to collect interesting photos from night-sky.

The researcher believe that this method might lead to new scientific findings, while working to engage the public in auroral study. After all, it was the beauty of 3D imaging of auroras that inspired Kataoka to create a new gadget for scientific research in the first place.

Source: EurekAlert!

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