Mike, I think you'll find that Ed William's algorithm (taken from the Nautical Almanac Office Almanac for Computers, 1990) is a simplified one using constants tailored to 1990 sunrise/sunset.
The generalised algorithm is rather more complex. See e.g. Jean Meeus’ Astronomical Algorithms.
Mike, I think you'll find that Ed William's algorithm (taken from the Nautical Almanac Office Almanac for Computers, 1990) is a simplified one using constants tailored to 1990 sunrise/sunset.
The generalised algorithm is rather more complex. See e.g. Jean Meeus’ Astronomical Algorithms.
You can see the differences analysed at http://eng.climate.com/2014/04/02/astro-algo-astronomical-algorithms-for-clojure.