Looked at some different dates.
Worst case found during a cursory search was @10 minutes in time which
came
out to about 2 degrees (on one side.)
You are right. Should have checked different dates.
Embarassed but wiser,
Tim K3HX
On Sat, 22 Sep 2001 20:33:21 +0000 alsopb <alsopb@gloryroad.net> writes:
> Look at some different dates. Today is the beginning of fall and the
> error is minor. You will find errors up to 15 minutes. Also the
> error could actually be double since the error may put the shadow on
> the wrong side of true North. You'd end up "correcting" in the
> wrong
> direction.
>
> 15 minutes = 7.5 degrees. Thus a worst case error 15 degrees would
> be
> possible. Our isogonic is 8.5 degrees. This error can be larger
> than
> the correction itself.
>
> 73 de Brian/K3KO
>
> tttt ccccc wrote:
> >
> > Dear Pete N4ZR,
> >
> > Here we go again!
> >
> > I figure that about now you will be getting static from some
> poster child
> > for
> >
> > anal retentive syndrome about the inaccuracy of the "shadow"
> method.
> >
> > Here's some ammo:
> >
> > I'm a serious amateur astronomer and it is really important to
> know where
> > north
> >
> > is for telescope alignment purposes.
> >
> > I've got a US Navy celestial navigation program which I've used
> for
> > years. (it
> >
> > runs on DOS so it works......every time, never locks up, never
> burps or
> > gives me
> >
> > messages about how stupid I am....HI!)
> >
> > Anyway, I looked you up on the DX Cluster's Buckmaster listing and
> ran
> > sunrise,
> >
> > transit (also called solar noon.....the time when the sun is due
> south)
> > and sundown
> >
> > for 22 Sep 2001 at your QTH. You may use these to contrive an
> offset
> > from the
> >
> > times given in the paper.
> >
> > Converted to EDST:
> >
> > Sunrise 0700
> >
> > Transit 1305
> >
> > Sunset 1908
> >
> > If you split the difference , you get 1304 as the middle of the
> day.
> >
> > OH, THE HORROR!!
> >
> > I ran a position for the sun at your QTH at 1304 and it is 179.7
> degrees.
> > Or about
> >
> > 3 tenths of a degree from due south. There are several factors
> that
> > contribute to this
> >
> > offset, the most prominent is that the earth has traveled in the
> orbit
> > about the sun
> >
> > during the day.
> >
> > Another source of joy for the "picky-picky" crowd is the fact that
> the
> > sunrise-
> >
> > sunset times are typically for an airport which may be some
> distance
> > away.
> >
> > Trivial. Perhaps a degree or so......no big deal.
> >
> > Considering the relatively broad bandwidths of HF and VHF beams,
> it seems
> > that
> >
> > the "shadow" method is PLENTY accurate enough.
> >
> > Polaris is a pretty good way to find north but this method may
> involve
> > climbing the
> >
> > tower at night. Also, the maximum "error" for Polaris is about 44
> > arcminutes or
> >
> > something just less than .75 degree. There are times which can be
> > predicted
> >
> > when Polaris is either directly north or south of true north
> (upper and
> > lower
> >
> > culmination) but again, for ham purposes, it is a bit much.
> Telescope
> > folk, however
> >
> > really have to be on the button or things will "drift" out of the
> field
> > of view.
> >
> > Well, have to boogie. Our astronomy club is having a public "star
> party"
> > tonight and
> >
> > I can't wait to wow 'em with my new, fairly big (yup.....size does
> > matter.....HI HI!!)
> >
> > refractor.
> >
> > 73
> >
> > Tim K3HX
> >
> > Cw Elitist
> >
> > QRP Snob (except on 160 where I run an amp in a futile attempt to
> > compensate
> >
> > for a really short antenna with a really crummy
> ground screen..HI!)
> >
> > Old Fart QRV 1964
> >
> > 20 WPM Extra Since 1986
> >
> > Draft Dodger Enlisted within weeks of turning 17
> >
> > Zoomie USAF 66-70
> >
> > Weekend Warrior OH Air Guard 71-72
> >
> > On Sat, 22 Sep 2001 08:55:48 -0400 Pete Smith
> <n4zr@contesting.com>
> > writes:
> > >
> > > Awww.... the true North thread is reborn.
> > >
> > > Maybe we can nip this in the bud. Get your local paper and find
> out
> > > when
> > > local sunrise and sunset are. Split the difference. When that
> time
> > > arrives, go down to the tower and see which way its shadow
> points.
> > > That's
> > > true North.
> > >
> > > 73, Pete N4ZR
> > >
> > >
> > >
> > >
> > >
> > >
> > > List Sponsored by AN Wireless: AN Wireless handles Rohn tower
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> > > supporting towers up to 100 feet for under $1500!!
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> > >
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> > >
> >
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