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    Azimuth and Declination formulae
    From: Peter Fogg
    Date: 2005 Jul 15, 10:29 +1000

    Peter Fogg wrote: (I did!)
    > Have found this one: (Azimuth formula)
    > Chuck Pettis' Azimuth equation:
    > AZ = acos ((sin D - (sin L * sin H) / (COs L * COs H))
    > where  H = horizon height (degrees)
    > (The H has me puzzled. Perhaps it refers to Dip, or could it refer to
    > altitude?)
    > Here's another:
    > Z = cos^-1 * [sin Dec - sin Lat * sin h / cos Lat * cos h]
    > where h = vertical angle to the sun corrected for parallax and refraction
    > (h = altitude?)
    I think they are the same sine method.
    The first version may be for terrestrial navigators, with its added factor
    of 'horizon height'.
    Along the way, I found a formula for the calculation of the Sun's
    Dec = 23.45 sin (360/365.25)
    Its such a simple formula even I can understand it. Its the maximum
    declination of the sun expressed as a proportion of its change.
    Here's another version:
    Dec/23.45 = sin(0.985*t)
    0.985 is a truncated version of (360/365.25)
    and t = the number of days from the vernal equinox
    t = (inv sin(Dec/23.45))/(360/365.25)
    These formulae come from:

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