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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
declination:

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
or
t = (inv sin(Dec/23.45))/(360/365.25)

These formulae come from:
www.geomancy/org./sunfinder

```
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