# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Azimuth and Declination formulae
From: Fred Hebard
Date: 2005 Jul 14, 22:35 -0400

```On Jul 14, 2005, at 8:29 PM, Peter Fogg wrote:

> 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

It's more accurate to use the length of the season as one quarter of a
circle, but even then there are errors.  The reason for this is that
summer is longer than winter, about 93 days versus 87.

```
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