Re: Auroras

[erker@xxxxxxxxxxxxxx (Greg Erker)]

John B. wrote:

>  I don't know if there is a film fast enough that isn't so
>coarse-grained that you would lose too much detail.

  I have a hazy recollection of a TV show about auroras
where they had some low light camera and said it was equivalent
to something like 12000 speed film.

  So even if you could get a film like that, it would be very
grainy, especially when viewed in 3d. And since there are no
sharp edges for your eyes to lock onto the grain would appear
even worse.

  And yes auroras sometimes do move very fast: ripples moving
across 20 or 30 degrees of the sky in a few seconds. So time
exposures wouldn't help you with these. The sheets that cover
large angles usually move slower but would probably be boring
in 3d anyways.

>  I remember it taking quite a bit of
>time (45 min?) for the eyes to dark adapt enough to even see anything,
>if that's a clue to their brightness.  Well, I guess you could see
>_something_ in 15 minutes and all you were going to see in 45.

  They are usually fairly dim, but bright enough for colour
vision. And sometimes they are bright enough to see from inside
the city (Saskatoon: population 190,000 and perhaps 5000 street
lights).

Greg Erker in the great white north (snowing today), land of
auroras




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