As I am an astro-imager I am quite familiar with the stars and planets
and routinely use them to verify the alignment of all of my HF and VHF
antennas on different towers. It is very easy to get precise second by
second positions of the sun and moon in programs like WSJT which I use
for VHF MS QSO's.
It is easy to step away from the tower and sight the moon, available
planet, or even sun esp if it is partially hidden behind some thin
clouds etc to verify within a degree or two the antenna alignments. I
have also done this at night with dozens of various stars since I have
access to programs that give me the precise azimuth and elevation data
on a real time basis.
Give the moon, sun or north star a try, it might surprise you. If you do
use the north star keep in mind it is off the true NCP about 1/2 degree
and you need to look up when Polaris hits either it's upper or lower
culmination points (the time when Polaris will be true north but 1/2
degree above or below the NCP).
Gedas, W8BYA
Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 12/25/2014 9:00 AM, Larry wrote:
You might be able to get North from your property survey in some
places. I am fortunate that the road in front of my house is a couple
of seconds off exactly E-W and my property only a couple of seconds
off N-S.
I have done the stick approach with good enough accuracy for HF beam
heading at QTHs at 35N and at 45N. True noon takes a bit of figuring
as very few places will have true noon coincide with noon on your watch.
USGS maps are another way of getting close to your lat/lon and which
way is N (or S or ...). Google Earth has been mentioned earlier. Many
counties have aerial photos of properties for tax purposes which may
indicate actual location and/or directions.
73, Larry W6NWS
-----Original Message----- From: Jim Lux
Sent: Thursday, December 25, 2014 8:31 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] north
On 12/24/14 10:39 PM, Spencer wrote:
In the northern hemisphere, the shadow of a vertical object at solar
noon will point north.
I've done all these North finding techniques over the years as kind of a
hobby activity (and sometimes professionally, too)
In mid-latitudes the shadow and stick works fairly well, although it's
hard to get sub-degree precision (for your North facing owl?) because of
several reasons:
1) The stick has to be vertical to within the accuracy of your desired
measurement.
2) the sun is half a degree wide, so the shadow edges are indistinct
(you could check this in a few weeks, if you shave the groundhog first,
so the fur doesn't cause the indistinct edge)
3) the sun moves pretty fast, so it's hard to tell the exact instant of
solar noon. The earth turns a degree in 4 minutes. Of course, you
don't need a precisely aligned antenna to receive WWV, and, knowing your
longitude, you can calculate when solar noon is. (don't forget the
"equation of time")
4) the shadow is pretty short at noon unless you're well north (in the
summer).
At 34 degrees north, in the summer (prime tower building season), the
shadow is pretty short. The sun's only 10 degrees from vertical at the
solstice. At La Paz or Los Cabos, Baja California, on the solstice, the
sun is directly overhead at noon (or so close you won't be able to
easily tell the difference)
It's MUCH easier to get north if you mark the shadow periodically.
You'll get a curve that you can then use to determine north.
What you do is make a smooth curve of shadow position during the day.
Then, you take a string from the *top* of the stick and scribe a semi
circle across the curve of constant radius. Draw a line between the two
intersections of curve and semicircle. The perpendicular bisector of
that line faces north/south.
(you still have the 1/2 degree width of the sun to contend with, and the
ground has to be level within a fraction of a degree, etc.)
If you're "between the tropics" (of Cancer and Capricorn) the shadow
goes both north and south, depending on the time of year. Think of a
stick on the equator: from March equinox to September equinox, the sun
goes north, so the shadow is south, and from September to March, the sun
goes south.
And for hams aligning their rotor in midwinter in the far north? No
shadow at all.
By the way, the north star (Polaris) is about 3/4 degree from true
north. It moves around the true pole in a circle. You can look up the
position at a given time/date, or watch it in a telescope and look for
culmination.
Moral of the story: getting true "north" to even one degree accuracy is
harder than it seems at first glance.
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