Colour video recordings of aurora

A new generation of semi-professional digital video (DV) camcorders have proved sensitive enough for almost real-time recordings (3-4 frames/s) of auroral phenomena [Brändström et al., 2003; Yamauchi, 1999]. One such camera (Sony DCR VX-2000E PAL) was procured by the author. The sensitivity for auroral scenes at 3 exposures/s was found to be of the same order as the unaided human eye (i.e. roughly 1 kR at 5577 Å). Several hours of auroral footage were recorded and the image quality is acceptable for TV-broadcasting and auroral visualisation for the general public (for example Swedish Television has broadcasted such material on two occasions). It has proved possible to record weak diffuse, pulsating and black aurora with an acceptable signal-to-noise ratio. These cameras could therefore be a good tool for studies of auroral morphology and dynamics, as well as for providing supporting images for other instruments (ALIS, EISCAT, etc.). Another interesting future possibility is to use this type of camera together with methods for automated image analysis as described by [for example Syrjäsuo, 2001; Rydesäter, 2001] for automated control over spectroscopic imaging systems like ALIS. The following table summarises some of the features of the camcorder tested:

• 3 CCD $\approx 450$ kpixels.
• Optics: $f=6-72$ mm 1:1.6-2.4
• $12 \times$ optical zoom, $48 \times$ digital zoom.
• miniDV tapes (memorystick for still-images)
• IEEE-1394 ``Firewire'' capture directly to a computer.
• Colour auroral imaging possible from about 3 images per second up to video rate, depending on auroral intensity. Good sensitivity for Red and Green auroras, acceptable for blue.

A sample frame of an auroral scene with a meteor trail is displayed in Figure C.3. Video footage can be made available by the author on request.

Figure C.3: Sample frame from a auroral video obtained with a commercial mini-DV camcorder displaying green, red and blue aurora. A meteor-trail is seen in the lower middle part of the image. A digital version of this image can be downloaded from: http://www.irf.se/~urban/28am