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Sunrise/Sunset Calculations where the positive number corresponds to sunrise, negative to sunset. Then the UTC time of sunrise (or sunset) in minutes is: sunrise = 720 – 4*(longitude + ha) – eqtime where longitude and hour angle are in degrees and the equation of time is in minutes.
How are the times of sunset and sunrise determined? A. Sunset and sunrise have exactly the same definition: the time when the apparent uppermost ray of the Sun is on the astronomical horizon. If it is the first ray, it is sunrise and if it is the last ray, it is sunset.
The sunrise and sunset times meet up and are exactly 12 hours apart.
I like to keep track of sunrise and sunset times. For the past couple of years I've been doing this with a small program written with a popular library for my favorite programming language. The last two months I've been keeping track of these times more regularly than usual, and I happened to notice that on the day of the equinox the sunrise time jumped eight minutes as compared to the day before! I knew this was impossible and compared with NOAA, finding out that my rise and set times had been off for several days and in fact seemed to be off by about a minute for most of the year.
At this point, I'd like to just implement the calculations myself. What algorithms or formulas are available to do this computation?
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