Stephen wrote:
> I'm wondering if someone has become an expert on the SUNPOS.inc and could
> shed a bit of clarification on its use as I'm a bit confused.
> I have read the reference material which is quite comprehensive, and now I'm
> looking for the "Dummies Guide".
> 
> I rendered an "earth" with equator and latitudes and longtitudes and placed
> a bump on it for my city (Calgary, Canada) which is roughly the same
> latitude as Greenwich, except -7 time zones (longtitudes).  I can never get
> the sun to be positioned where I would expect it, specifically
> 1) over the  Equator on March and Sept 21
> 2) over the Tropic of Cancer June 21
> 3) over the Tropic of Capricorn Dec 21
> 
> If I rotate the earth by  rotate x*23.5 which is the declination of this
> rock, the apparent position of the sun changes accordingly, but again
> nothing lines up.
> I'll happily share the source but I'll have to clean it up a bit first.
> 
> I'm wondering if someone has already explored this field recently.

Have you been careful about the input values?
Your inputs for the vernal equinox would be something like
SunPos(2004, 3, 21, 12, 0, -105, +51, -114)

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