Re: PHOTO-3D digest 1245

[harold lee tichenor <hticheno@xxxxxxxxx>]

> John W Roberts <roberts@xxxxxxxxxxxxxxxxx> wrote in photo-3d 1245
> 
> There's another celestial phenomenon (and one for which *real* stereo
> photography would be possible) for which I have a similar problem - the
> aurora. 

In 1966, I worked for the Geophysical Institute at the University of Alaska 
on a project designed to photograph and measure the aurora.  We had several 
photographic systems including an all sky camera that used a 35mm Mitchell 
NC and a short focal length lens.  My job was to get the Mitchell up and 
running and assist in building a time exposure motor control for it.

We also had half a dozen 16mm cameras in remote locations from Fairbanks to 
Watson Lake in the Yukon, a distance of about eight hundred miles.  During 
auroral displays we could trigger all six cameras at once and then collect 
and process the six films which could be run simultaneously in sync.  From it 
we could triangulate and map the individual display. (Effectively a series of 
stereo bases from about 100 miles to 800 miles!) 

Normally the "curtains" shift at a moderate speed just perceptible to the 
eye. Occasionally, there are rapid sweeps that stretch from horizon to 
horizon in a matter of seconds.  The effect is caused by bombardment of the 
ionosphere from particles emitted from solar activity, sunspots.  The 
particles hit the ionosphere and rapidly oscillate from pole to pole creating 
matching auroral displays around both the North and South Magnetic Polar 
regions.  Generally, because only one pole is in darkness at any given time 
the display is only visable at one pole; however I believe there are now 
photographs taken by NASA that actually show the matching auroral displays.

The black and white motion picture film stocks we had thirty years ago were 
too slow for us to operate the motion picture cameras at the standard 
24frames per second (e.g. 1/50 second exposure time).  So we had to 
undercrank.  I believe we were exposing at one frame per second with a 
shutter speed of 1/2 second, and an ASA of 400.

Harold



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