John Schilke
Thu, 01 Jul 2010 13:39:53 -0700
On 2010 July 1, at 10:12, John Goodman wrote:
I'm looking for a simple formula which calculates the number of
hours that the sun will be above the horizon on the summer solstice
for any given latitude. I don't need to worry about refraction, or
take into account the sun's diameter. I'm just interested in the
simple geometric case, using the center of the sun's disk for
determining the start and end times.
For my purposes, these simple relationships will be true: If the
answer for summer solstice hours is SSH, then winter solstice hours
will be 24 - SSH, and equinox hours will be 12, regardless of the
latitude.
John,
It would seem simplest to use the old formula
cos T = – tan φ tan δ
(latitude and declination, respectively)
then, H (hours above the horizon) = 2 arc cos T, approximately.
That is, in fact, how I usually do it, quickly and easily.
Your other statements are correct.
Best wishes,
John
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