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Those imagers without a filter wheel, such as the ones that will be used in NASA's THEMIS, use sensitive modern CCD-cameras. These so called white light cameras still produce grayscale images, because the camera itself is of black and white type. The Institute for Space Research at the University of Calgary has already deployed 15 out of 16 THEMIS imagers. in Canada. We are developing a colour auroral imager to support our research in automating auroral image analysis. We have named the imager RAINBOW (probably just to confuse everybody...) |
Real-time images from Nyrölä, Finland. Hopefully it is clear and we see auroras...
To illustrate the difficulties in analysing grayscale images, here are two images captured at the Athabasca University Geophysical Observatory almost simultaneously with a THEMIS prototype camera (left) and RAINBOW (right). The fields of view are slightly different as are the orientations of the images. Nevertheless, both images show an auroral display behind the clouds. The bright spot slightly right of the centre is the Moon. There is some bright aurora in the lower part of the images. Notice how distinctive the green aurora is in the colour image. The grayscale image on the left does not provide enough information alone: you need to use several images and verify the movement of the aurora before you can be sure. |
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Auroras far in the north... 21 February 2004. Images are from Longyearbyen (Norway). |
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Really nice auroral display on 25 July 2004. Images are from Athabasca (Canada). |
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Wonderful auroras on 9-10 November, 2004. Images are from Athabasca (Canada). |
The movies below are in Quicktime-format and can be played in Macs and Windows-computers using Apple's Quicktime player. For Linux and other Unix-flavoured systems, you can use xanim to view the animations.
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A QuickTime-movie (about 4.0MB) showing nice noctilucent clouds captured on 16th of July 2005 in Nyrölä (Finland). North is up and east is to the right. Each individual frame is a 0.5-s exposure originally captured at every 10 seconds. |
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A QuickTime-movie (about 2.0MB) showing the first auroras in Nyrölä (Finland) on 24th of August 2005. North is up and east is to the right. Each individual frame is a five second exposure originally captured at every 10 seconds. |
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A QuickTime-movie (about 1.6MB) showing the first bright auroras in Nyrölä (Finland) on 31st of August 2005. North is up and east is to the right. Each individual frame is a five second exposure originally captured at every 10 seconds. |
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A QuickTime-movie (about 15MB) showing one rare clear evening in Nyrölä during the Autumn 2005. Because there were no auroras, the scaling is enhanched to show the Milkyway and the stars. North is up and east is to the left. Each individual frame is a five second exposure originally captured at every 10 seconds. |
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This autumn's first auroras!!! QuickTime-movie (about 12MB) shows auroral arcs and pulsating auroras. Each individual frame is a five second exposure originally captured at every 10 seconds. |
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Very nice auroras on 14-15 of December, 2006. A QuickTime-movie (about 12MB) shows plenty of colour and lots of action. Each individual frame is a five second exposure originally captured at every 10 seconds. |
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The lunar eclipse on 3-4 Feb 2007 as captured by RAINBOW. The QuickTime-movie (about 4MB) shows the darkening of the moon due to the Earth's shadow. Each individual frame is a five second exposure originally captured at every minute. |
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A QuickTime-movie (about 5.0MB) showing nice noctilucent clouds captured on 21st of July 2009 in Nyrölä (Finland). North is up and east is to the right. Each individual frame is a 0.5-s exposure originally captured at every 10 seconds. |
Almost all auroral imagers used for scientific purposes are
essentially black and white cameras. The majority of these imagers use
a filter wheel with a number of optical filters. This provides
information of selected wavelengths, which is what most space
physicists want. The brightest auroral colours are yellowish green
(wavelength 557.7nm) and red (630.0nm).