Name: Daniel B.
Date: Thursday, September 12, 2002
I am trying to find two algorithms for a computer program that I am
working on. I need to be able to calculate the times when Nautical
Twilight, and Civil Twilight begin and end.
If you can give me an answer to this question, I would really appreciate
it. Thank you.
Definitely the place to start is the web site:
http://aa.usno.navy.mil/data/ which provides the information you seek.
However, I did not search the links to find out how they arrive at their
results. The earth undergoes some 10 or 12 different oscillations, wiggles,
rotations, tidal effects, etc. due to various small, but measurable
interactions. I suspect that USNO arrives at their times by a rather
complicated algorithm, that probably even contains some empirical
corrections. You might contact them and see if they can point you in the
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