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Re: shortest twilight problem...
From: John Huth
Date: 2010 Jun 29, 11:57 -0400
From: John Huth
Date: 2010 Jun 29, 11:57 -0400
Marcel -
That makes sense. At the poles, you'd have several days of twilight, if you defined it to be the length of time the sun was in a certain angular range below the horizon, and, in fact, this would be around the equinoxes. There are interesting limiting cases.
John
On Tue, Jun 29, 2010 at 11:48 AM, Marcel Tschudin <marcel.e.tschudin@gmail.com> wrote:
The day of shortest twilight actually does depend on latitude. The
attached graph shows the durations at the equator. The conditions are
the same as for the graph at 41 deg latitude. At the spring equinox
the minimum for the morning twilight is on 20 MAR 2010 and for the
evening twilight on 18 or 19 MAR 2010 (same duration in seconds). At
the autumn equinox the minimum of the morning twilight is between 21
and 24 SEP 2010 (same duration in seconds) and the evening twilight
between 20 and 23 SEP 2010 (same duration in seconds).
I guess the challenge must have been to calculate how this depend on
the geometrical parameters.
Marcel