[TowerTalk] Positoners Calibration to True North

[AD5VJ Bob]

Also since you wanting precise measurement for sat work I
just found out from reading that Mag north changes all the
time so you might want to use this link for more accurate
readings and subsequent periodic adjustments to your
calibration mechanism:

http://geomag.usgs.gov/observatories/data/realtime/



  73 fer nw,
Bob AD5VJ

10X# 37210, FP#-1141, SMIRK#-5177
http://www.n5iet.com/
Code may be taking a back seat for now,
but the pioneering spirit that put the code
there in the first place is out front of it all.




> -----Original Message-----
> From: towertalk-bounces at contesting.com 
> [mailto:towertalk-bounces at contesting.com] On Behalf Of
Jim Lux
> Sent: Thursday, December 01, 2005 10:54 PM
> To: Tom McAlee; towertalk at contesting.com
> Subject: Re: [TowerTalk] Positoners Calibration to True
North
> 
> 
> At 08:15 PM 12/1/2005, Tom McAlee wrote:
> >Since the original question was posted by a VK station,
it might be 
> >worth noting that using Polaris to locate north can
only be 
> done in the 
> >northern hemisphere.  It is not visible below the
equator.
> >
> >Down there you'll need to locate south and flip that
180.  
> But, there 
> >is no "south star" such that the south end of the
earth's 
> axis points 
> >almost directly at it.  But, there is some bizarre
combination of 
> >constellations/stars and drawing lines and following
them 
> >perpendicularly to other stars, etc., that can be used
to locate the 
> >south pole with enough accuracy for antenna work.
> >
> >But, never having been in the southern hemisphere, I
don't know the 
> >details. I'm sure you can find info about it on the web
though.
> >
> >And, by the way, Polaris isn't exactly north; it's
about 1 
> degree off 
> >true north.
> 
> 
> use the SUN.. at local solar noon, the shadow will
either be 
> directly north 
> or directly south.  The trick is figuring out when local

> solar noon is. 
> Fortunately, you probably don't need to know to the
gnat's 
> eyelash second 
> of arc accuracy.
> Noon is when the shadow is shortest, but if you mark
where 
> the shadow is 
> equal lengths, the north south line is exactly halfway
between.
> 
> Jim 
> 
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