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Name: Daniel B.
Status: student
Age: 15
Location: N/A
Country: N/A
Date: Thursday, September 12, 2002


Question:
Hello,

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.


Replies:
Daniel

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 right direction.

Vince Calder



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