[Antennas] Using GeoClock To Find True North

[Charles Greene]

At 12:39 PM 2/18/2002 -0500, Merv Stump wrote:

Merv,

If you are in the Northern hemisphere, use the North star.  I line some 
local landmark up with it, then use the local land mark during the day.  If 
you actually want to use the sun, there are some nautical almanacs that 
give you the time of local apparent noon depending upon what your longitude 
is and what day it is.  Local apparent noon is when the sun is crossing 
your longitude line and is directly South.  Another way is that if you have 
a sextant or other means of measuring the sun's altitude, it is highest at 
local apparent noon.

>The ARRL Antenna Book describes a method for finding true north based on the
>fact that the sun is directly south at 12:00 noon local time.  This is of
>course only true if your qth is exactly on the longitudinal meridian on
>which your time zone is based (e.g. 75 degrees for EST); and on the dates of
>the summer and winter solstice.  For any other location and on any other
>dates, corrections have to be applied to determine the exact time at which
>the sun is in the south.  The antenna book explains how to make these
>corrections.  However, I just noticed that GeoClock gives you the azimuth
>and elevation angles for the sun at all times.  When the azimuth angle is
>180 degrees, the sun is in the south.  Today at 12:08:40 I ran to see if my
>boom lined up with the shadow of my tower.  It's a little off, and now I'll
>have to worry about it until spring.
>
>Regards, Merv

73, Chas, W1CG