Hello, everyone,
Slightly off-topic, but fun :
New Scientist magazine for 2008-10-04, page 46, features a solargraph -
an image that shows the track of the sun's position over time - that was
made using a pin-hole camera pointed at the Clifton Suspension Bridge in
Bristol UK. The image was c
Brent,
Have a look at http://en.wikipedia.org/wiki/Decimal_time - French
Revolutionary Time and Fractional Days both seem to have a bearing on
your Angular Clocks.
Why go with 100 degrees in a day? Radians are a well understood, and
completely suitable alternative. Lunchtime would become Pi
Hi,
I sometimes use a spreadsheet to calculate a series of X,Y points, and
then use these points to create a scattergram chart. My problem is that
whenever I do this, the chart appears on the screen as a rectangle. The
X and Y dimensions aren't to the same scale. I have to set the gridline
in
On 12/08/2011 6:21 AM, Richard Mallett wrote:
There is a paper in Nature that describes the Nabta Playa calendar
circle (and maybe other stuff) :-
Malville, Wendorf, Mazar and Schild "Megaliths and Neolithic Astronomy
in Ancient Egypt" Nature 392 (488-490) 1998
How do I get a copy of this pa
On 15/08/2011 3:52 PM, karon wrote:
the smaller [sundials] are, by definition,
the less precise they can be.
This statement got me wondering how small can a sundial be, before
hitting the limits of our visual acuity. Here's my thinking:
Shadow blur imposes a limit of about 2 minutes of tim
uestion:
are there other examples of sundials being used even today, to measure
the passage of time for ‘real world’ purposes?
Steve Lelievre
Fredericton NB
Canada
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
All,
I too have tried Bob's method of diverting HPGL printout to a file. I then
used an HPGL viewer to look at the resultant diagram.There's something odd
which I don't understand: The original diagram uses several line width, the
plot file lines all look the same. Also, the original diagram has
A few days ago I asked questions about the appearance of a DeltaCad drawing
which I had sent to an HPGL plot file using the method posted by Bob
(putting an HP5785A on a file redirection device ). I have investigated
further using the HPGL information provided by Thibaud T-C and viewer advice
from
In response to a mail item from Mac and a posting by Fer asking for more
code to be shared, I have decided to publish my DeltaCad macro for plotting
horizontal Standard Time dials, (the type that are drawn by Fer's "SPIN"
program). You can choose either azimuth or polar-axis style. The program is
Peter,
As I mentioned in my earlier note, I took out Southern Hemisphere support
while I struggled to understand how your dials would look. I'd still
appreciate answers to my earlier note, but in the mean time I've posted a
new version of SCADD that does accept SH coordinates and caters for your
John,
> The gnomon on your dial is a verticale pin at the center of the cross,
> and half as tall as the cross, right?
Not sure which case you mean. In the polar-axis case, you're making a
Horizontal Dial. The gnomon climbs at an angle from the centre of the dial
(the centre of the cross). It yo
John,
The NASS site has some DeltaCad macros.
As regards how big to make the dial, I suspect that people size will not be
a meaningful starting point. In the extreme case, there is hardly any
shadow.
Your dial is S.Calif - say about 33 and a bit degrees N. At the Summer
solstice, the sun at noo
I'm trying to convert an azimuth value into an hour-angle, and would
appreciate some help with the formula and with my algebra. Using
dcl=declination, lat=latitude, azi=azimuth,ha=hour-angle, I started with a
standard formula for azimuth given hour-angle:
tan(azi) = sin(ha)/(sin(lat)*cos(ha) + ta
Thanks to Jorge Ramalho for pointing out a sign error in my last message. It
should have read as below. I still have the same questions, tho'
Steve
I'm trying to convert an azimuth value into an hour-angle, and would
appreciate some help with the formula and with my algebra. Using
dcl=declinatio
Bill, John, and others,
Thanks for your replies. I'll read and absorb.
Steve
Gordon said:
> > From Jean Meeus's "Astronomical Algorithms," 1951, p. 89:
> >
> > tan H = sin A / (cos A * cos f + tan h * cos f)
> >
> > where H is hour angle, A is azimuth, f is latitude and h is altitude,
> > and H is obtained via the arctangent.
to which Bill said:
>
> But note that i
- Original Message -
From: "John Carmichael" <[EMAIL PROTECTED]>
>I think it would be more useful for a sundial designer to have the table in
a
> more useable form that lists the maximum distance of visibily for
different
> widths. (I picked 1/16 inch increments because these are the size
For your info:
There is an article in the most recent edition of Sky and Telescope magazine
about "photographing the analemma".
It describes how photos have been taken which show the movement of the sun.
They rely on time lapse (either 365 or 12 exposures over the course of a
year), with each ex
I reckon the state of the tree is a clue too. It looks deciduous to me, so
we ought to see exaggerated dark veins due to bare branches from the winter
part of the image. The branches will be displaced by winds, so the tree
ought to look blurred. The dark blue sky and dark shades of green in the
tr
- Original Message -
From: "John Carmichael" <[EMAIL PROTECTED]>
To:
Sent: Tuesday, February 15, 2000 12:27 PM
Subject: Dali dial rings & gnomons
> HI all:
>...
>Apparently, ring order and number of
> rings are not important. Am I correct?
>...
> I know we discussed the Dali azmuthal d
At present, I can't see any reason why the wriggley lines of the Civil Time
adjusted Azimuthal dial (a.k.a. Dali dial) should not apply to other types
of dial, thus eliminating the need for an Equation of Time plaque. Using the
Horizontal dial as an example, if the 12 o'clock line were to wriggle
Art wrote :
>The flexibility of choosing the shape and location of the date
> rings remains (pro 1), so an Arizona dial, for example, is still
> possible.
I concur.
>Will one of you that has been
> posting azimuthal dial plate designs please plug in a polar gnomon for
> me?
>
> Are you interest
Gianni wrote:
>Since I could not call azimuthal these solar clocks (because they don't
have
> this characteristic even if their shape look like azimuthal) I have
> called them (in my program with which them can be calculated) "Monofilar"
> since the shadow is made only from one style or " t
Gianni wrote:
>The Monofilar and Bifilar sundials can be built with any kind of Time:
>Middle Time (Standard), Local Apparent Time, with Italic, Babylonian,
>Temporary hours, etc.
Ah ha! I must have misunderstood the issue being discussed.
I can see that in abstract terms that we have dials
>From: "Daniel Lee Wenger" <[EMAIL PROTECTED]>
> I should point out that my dial reads time by a
> projection of a point onto a point (the first point being on a surface)
Oops, I knew that...
> and that it reads standard time.
...but I didn't know that.
Apologies,
Steve
I'm relatively new to dialing, and indeed this is my first post to the
mailing list (but I've lurked here for a few months). I'm also a great
enthusiast for using "rules of thumb" in everyday life, but so far I've not
found many cases where I can put the two together. I'm hoping that this
posting
I have recently seen a couple of dials which use a nought (a digit zero) in
place of XII, whereas the rest of the hour labels are in their usual roman
numeral forms. In other words, they run VI, VII...XI, 0, I, II...VI. One
dial is from the 1950s and the other from the 1960s. They are both located
Fer wrote:
> In France there are a number of dials with the noon line labeled with M.
I guess the M is for something like midi or meridiem.
Can a Francophone please confirm.
Steve
I recently came across a sundial on a swivel mounting, and I don't
understand the purpose of the mounting. Can anybody enlighten me?
The location is Chester, Nova Scotia, on the waterfront. It is a
commercially produced dial in the form of an armillary sphere. I have seen
similar but slightly sim
Oops, in my last posting I was duped by my spell-checker into using the word
'gnomic' instead of the intended 'gnomonic', which the software doesn't
recognise. Hope I didn't confuse you.
Steve
Hi all,
It's only a few days to the equinox, which happens here in the middle of the
night (3:35 AST). I'm going to use the previous evening and following
morning to use a pole's shadow to make myself an East-West line, to compare
to my existing NS meridian line. I hope to find that they are at r
Jim wrote
> I used xephem 3.2.3 to solve for when solar declination = 0.0 and got
> 2000 March 20 7:30:59 UTC. Xephem calculates that the declination of
> the moon at that time to be 2:50:47.5 (degrees:minutes:seconds).
I take this to mean that the moon's plane of orbit is tilted too far from
Ea
Is there anybody out there with a program for creating azimuth dials, where
the program makes adjustment for a cylindrical gnomon, as opposed to a
line/wire, and where the time is read on the leading edge of shadow.
If so, please contact me by email to [EMAIL PROTECTED] as I would
like to check
John wrote:
> Which is better, DeltaCad or TurboCad? What's the difference?
I can't comment on the differences as I have only used DeltaCad.
I can warn you that there is a bug in DeltaCad which causes spurious error
messages when editing text items, if the screen resolution is 1280x1024 or
high
John wrote:
>{clipped}..I was very happy to find DeltaCad available online for only 39
dollars.
There is a 10USD shipping surcharge for destinations outside the USA. For
euro-zone buyers the total price equates to just under ?50 (or more if you
get caught for import duty).
Steve
The situation seems to be:
Illustrator costs about 400 USD+shipping, whereas DeltaCad is about 40
USD+shipping.
DeltaCad shares the basic facilities which Tony mentioned for Illustrator -
dilation, rotation, translation - but not the distorting operations such as
shearing and stretching text to
I sense a hint of sarcasm in this note, which I take to be an invitation to
shut up, which I shall now do - with apologies for boring the rest of you.
Steve
> I find this discussion very interesting, especially the tutorial on the
> fabrication process. My impression is that everyone involved i
Steve
You said:
> Certainly not intended, in fact I wished to join in from another
perspective.
Then I hope my reaction has not embarassed you.
> If you have a 3D CAD model, please send.
I do not have anything in 3D. Let's hope somebody else can post a drawing
for you.
I was banging on about
Bob wrote:
> While I have only had the demo version of DeltaCad for a few days, I
> have some observations. Perhaps others can provide
> more.
I have observed these problems with DeltaCad. Regards, Steve
1) If your PC graphics mode is 1280x1024 or greater, the functions for text
editing misbeh
Mac wrote
> I'm going to need a little help understanding this sundial, but the
> pinhole photography is very nice.
Me too. It's intriguing.
Why are the hour labels mirror images and run anticlockwise starting with 12
at the bottom? (or has the photo been accidentally mirrored about its
vertical
John asked:
>Does anyone know of a good source for computer fonts (preferably
Windows-compatible) of antique >characters
Adding to John's request, can anyone give me details (name, source of
download) of the British public sign font, used for most of the offical
signs in public places - the one
Ron,
Have you heard any dates for the next DeltaCad release, with the upgraded
dxf handling?
To all DeltaCad users,
For information, I just noticed that the DeltaCad site has a new patch for
version 4, dated 20th Sept 2000. (download from
http://www.deltacad.com/patch/patch.exe )
At last I'm
Following message forwarded to list on behalf of ++ron. Regards, Steve.
> Have you heard any dates for the next DeltaCad release, with the
> upgraded dxf handling?
>
> Thanks for reminding me. I have sent a note to Midnight Software asking
> about the DXF upgrade. I have also asked for a lis
I would like to take a design made under DeltaCad, and get it cut into a
brass plate. None of the local engravers can handle the job (they just do
little plaques for sports trophies). The only local millwright does not have
computer controlled cutting machines. The local signwriter can accept
elec
I just came across a photo of a water filled sundial at Herstmonceux,
England, but unfortunately there is no background information given. The
photo is at http://www.ualberta.ca/~droles/astro/astrav/Sun2.html
I can not find any information about this dial on AltaVista or Yahoo. Can
anybody provid
My wife tried to find me a shop-bought calendar with sundial pictures for a
Christmas present. No luck, so I'm thinking it would be fun to create one
for 2002, and post it on the Web.
My idea is to produce a MS-Word document (or perhaps Acrobat) with the usual
monthly grids and pictures, and a sn
This is a post scriptum to my last message:
If you've got any comments / input for this little project, please contact
me off-list.
Thanks, Steve
I want a stand for a small horizontal sundial, but the ornamental plinths
and birdbaths sold locally are expensive and would be rather hard to modify.
Getting something carved by a local mason is way beyond my means..
I'm thinking of making something myself by casting it in concrete. Addition
of
Willy said:
> The question of Frans Maes was not: "Give me a formula for the
circumference of an ellipse."
> but "Give me a NON-mathematical, intuitively convincing explanation for
the fact that
> there is no 'simple' formula for the circumference of an ellipse."
>
> I think we are mostly taked u
Thierry wrote:
>So it's not France who distinguishes from the rest, but ...UK who are the
sole
> to insist on 'their' GMT time (nowadays called UT).
>(I should check for Ireland, but I'm pretty sure they are on WET/WEST too.)
Ireland is on the same timezone at the UK, and so is Portugal. It seem
Somebody was kind enough to contact me with some improvements to my sundial
plotting macro for DeltaCad.
Unfortunately, I have accidentally deleted the mail item and can't remember
who the sender was.
Please resend!
Steve
Want to know who's going to win in your constituency?
Try my UK
In a recent edition of New Scientist, there is an headline which says that
sundial principles are being applied to satellites.
In seems that for the new generation of micro-satellites designers want to
avoid having lots of heavy on-board batteries, and so will rely on small
solar panels to provid
Gianni wrote:
> As in almost all Web sites, also you take as positive the Longitudes for
> places West of Greenwich.
> Despite the opinion of the known astronomer J. Meeus, with which also
Davis
> agrees in his Sundial Glossary, even if a secular tradition justifies this
> definition, it is NO
This is off-topic, but why are they called Arabic numerals? Presumably
because the system of positional significance is Arabic in origin?
Also, real Arabic digits look nothing like the digits in the West (see
attached for 0 to 9, Arabic style). Why and when did the differences arise?
Steve
---
A friend at the Nova Scotia Astronomy Society produced a do-it-yourself
cardboard sundial template for their 2000 annual weekend gathering. Several
hundred were distributed to attendees and it was later published in a
newsletter of The Royal Astronomical Society of Canada. The idea was
popular, a
There's something I don't understand about a compound portable dials. As I
understand it, a conventional horizontal dial can share its mounting plate
with an analemmic dial to form a self-southing dial. The user simply turns
the whole contraption until both dials read the same time. In this posit
Rohr mentioned an itinerant sundial maker in Austria, who roamed from
village to village making vertical sundials for inns and church walls. I've
been trying to imaging how would this person, or others in the same trade,
have gone about their business.
The construction part could have been fairl
Thanks for the various replies to my recent postings on self-southing dials
and also on the finding south when setting up a vertical dial. Apologies for
the delay in responding.
Regarding the posting about an itinerant C17th dialmaker, the consensus
seems to be that he would find south by the met
To all those who expressed interest in my sundial calendar project of a few
months ago, I have to inform you that I've decided not to go ahead with it.
It has turned out to be too difficult for me to gather enough material to
complete the project in the way I had envisaged.
Thanks to everyone wh
Hi,
A friend has sent me a couple of pictures of a sundial at Montegufoni in
Tuscany, and has asked me how it works. I can't figure it out fully.
On the face of it, we seem to have a fairly ordinary vertical decliner using
a nodus, but we don't understand the hour numbering. They don't seem to b
From: "Alain MORY" <[EMAIL PROTECTED]>
> hello,
>
> About canonical hours, I read that they were called so, while the monks
> had to sing their prayers in "canon". Did anybody read this ? More
> informations are better than only one.
Hi,
I looked on the Web for other sources of information to s
If my memory is of any avail, week days repeat at regular
intervals of 18 years. Maybe I am wrong. Anyway, it is
easy to check if you have a perpetual calendar at hand.
It should be 28 years (for 7 days in a week x 4 years between leaps)
Specifically, there are 52 weeks plus 1 day in a year,
With the recent talk of interval timers, I have to mention my swimming trip
timer.
My wife and I like to leave our watches at home when we go to the lake in
the summer. We want to get home at the time promised to those left behind,
but neither of us is good at sensing the passage of time. There i
I agree, John.
At one solstice the EoT is about +2 minutes, and at the other it is about -2
minutes so there would be only a slight discrepancy. Too small to worry
about, especially as this is a junior school project and Judith is trying to
avoid too much complicated explanation.
I like her appr
John Carmichael suggested floating the mirror in mercury to level it, and
then Dave Bell pointed out that the clean surface of the mercury could be
the mirror.
Since mercury is a bit of a problem to work with, could a dish of water
serve instead? In John's case, he just needs the mirror to be abl
John,
Isn't the problem down there in Tuscon that the water would evaporate before
any algae has a chance to grow?
As Gino pointed out, if one creates a dial by calculation, there may be a
problem transferring it to a room by measuring off, because walls and
ceilings aren't plumb true or may be
> Edley, Steve, Andrew, et al,
>
> Approximate 'trig.' from memory is all very well, but
> why not simple geometry of equality and bisection?
>
Because nobody ever pointed it out to me before !!
> With a string, twig, or weed-stem part as arbitrary
> unit-length b, swing a circular arc. Cut suc
I'm doing some research relating to Acadian material culture, and came
across a brief mention of domestic sundials. The reference is originally
from "Chéticamp, histoire et traditions acadiennes" (CHIASSON, Fr. Anselme,
1961, Moncton). There is a passage describing the construction, layout and
fur
Edley mentioned hearsay of a window dial, thus:
"[The source] said they carved out deep narrow notches which, when the sun
fully filled the notch, it was that particular time".
That's sounds very much like a shadow-plane dial, but reversed to use
illumination rather than shadow as the indicator
Thanks to everyone who replied to my question about the possible nature of
Acadian sundials - once again shadow planes dials have proven themselves to
be ratehr interesting.
The second part of the question remains open - if you know of locales where
time marks or sundials were routinely added to
Hi,
I have been contacted by a company of landscape architects who are
contemplating a large dial for a current project. I advised them to consider
using a sundial design consultant, since they don't have experience in the
art. I volunteered to help them find contact details for consultants, so i
I don't know how to find old messages for this list. I used to look at an
archive on Yahoo Groups (http://groups.yahoo.com/group/sundial/messages/),
but the last message there is from 2001/07/11.
Where else can I look?
Thanks in advance,
Steve
-
- Original Message -
From: "Mr. D. Hunt" <[EMAIL PROTECTED]>
.
> If anyone wants to visit one of our layouts in a public location, and then
> 'reverse engineer' it - I am perfectly happy for them to do so.
Oooh, there's nothing like a challenge! Unfortunately, in spite of their
apparent
Darn, I forgot something.
I was saying that I suspect Douglas Hunt doesn't bother to deal with the
"October" problem - but one way to do it would be to calculate the position
of Oct 1 and Oct 31 twice over (for each of the two dial sizes) then split
the difference. I think that would reduce the m
Since my PS has arrived back in my mail box, but my original posting has
not, I assume the original is lost in the ether. Apologies if this turns out
to be a duplicate. Steve
- Original Message -
Mr. D. Hunt wrote
.
> If anyone wants to visit one of our layouts in a public location,
Here's another answer which doesn't answer your specific question - remember
the old Scout trick:
Hold your watch level, and turn until the the hour hand points in the
direction of the sun. Mentally divide the angle between the hour hand and
12.
That's an approximate NS line. It's each to
Hi,
I haven't seen any reply to the John Close / Mac question. Did I miss
something? What's the verdict?
For my part, I can see that it would be possible to construct a 2D shape
(approximately oval), which when set in equatorial plane, would cast a
shadow giving a certain EoT adjustment - you wo
But wait a minute
...as soon as I'd sent my last message, I saw a problem with it.
The plane of the sun's orbit doesn't really change with declination, so my
way out of the problem of varying declination doesn't work - so I don't have
a solution after all!
Steve
-
Sara wrote (snipped)...
> One reader took me to task for my use of the word "corrupt" and perhaps
> others were equally puzzled.
Well, I for one had no problem seeing it as corrupt (modern). But if we
don't like corrupt, how about fraudulent?
The site says the dial is "...an authentic replica
Anselmo Perez Serrada wrote (in reply to John Hall)
> I thought it'd be unpolite to introduce
> cookies in some other people's computers. You know this is a
> controverted question!
If you're reluctant to use cookies, why not have a URL that can include lat
and lon? Users could (optionally) crea
Hi dialists,
This is a question particularly for those of you who have web sites.
Would be willing to willing to include some predefined keywords in your
sundial-related web pages, in order to make it easier for the rest of us to
locate sundial related web pages using search engines?
My problem
I think the sundial situation is different to Bill's situation. He
deliberately introduced a spelling error in an attempt to create a unique
keyword which would be all his own, and was confounded when the search
engines 'helpfully' started to correct close matches. I'm just asking for
pages to inc
Gianni wrote:
> For a hypothetical inhabitant of the Pole (that would have to be extremely
> thin and threadlike) it doesn't exist any astronomical phenomenon that can
> be used to mark the beginning of the day or the instant from which to
start
> a whatever system of hours.
There isn't? There is
Chris wrote:
there is a point at the pole at which the height of the sun does
not vary during the day...
Ah. I looked at my globe again and I see where my visualization was wrong.
My revised thinking is that actually the sun's height does vary during every
day due to declination. During th
Stonehenge Aotearoa is a latterday henge in New Zealand, just opened to the
public.
It isn't quite a sundial, but it has an analemma (see pic half way down web
page), solstice markers and equinox markers, and stuff to do with polynesian
star navigation.
http://www.astronomynz.org.nz/stonehenge/s
Thanks,
Steve
Steve Lelievre
Halifax, NS
Canada
-
titudes, which are seldom a factor with sundials.
Best regards,
Jim
From: Steve Lelievre <[EMAIL PROTECTED]>
Date: 2005/03/27 Sun PM 03:29:54 EST
To: sundial@rrz.uni-koeln.de
Subject: Azimuth to Hour Angle code wanted
Hi,
I'm looking for some BASIC code (or, second-best, C code) that
John,
If it's in North America, you can use Google
Maps.
Go to http://maps.google.com
Type in the location into the search box, using a
format like "44.0n 63.615153w". When the map
comes up, zoom in or out until you see the town name.
There's a cool satellite view facility - look
Oh, and Google maps takes this format
too:
44 40 00n 63 36 55w
Steve
Richard Langley wrote:
A Canadian $10 silver coin to be launched today celebrating the Fortress of
Louisbourg includes sundial numerals along its circumference alluding to
the
sundial that was found during an archaeological dig at the historic sight.
You can see a photo of the face of the ex
On 15/10/2012 10:48 AM, brick...@62bricks.com wrote:
Online content that is blocked for certain regions can be viewed using
a proxy service. There is a simple program called Tunnelbear,
available at http://tunnelbear.com , that will allow you to view
content that is restricted to the UK. You ju
On 18/03/2013 6:30 PM, Darek Oczki wrote:
Dear Friends
I am looking for two articles by Tadeusz Przypkowski:
1. The gnomonics of Nicolas Copernicus and of G J Rheticus, Actes du VI-e
Congrès International d'Histoire des Sciences, Pages 400-409. Florence 1956.
2. Gnomonics of John Hevelius, Act
Hi all,
What, if any, is the significance of the recumbant crescent in this
dial? Wikipedia describes crescents in art and symbolism, but its
description relates mostly to the crescent as a symbol of Islam and in
Christianity (Roman Catholic) as a symbol for Mary.
Is there any other or more
On 06/07/2013 8:38 AM, Barry Wainwright
wrote:
It can be done, but how the characters are rendered depends very
much on the application used to render them.
There are a block of unicode characters called "Combining
Diacritica
Bishop Olaf reported that the people in some part of
northern Scandinavia use staffs inscribed with markings which measured
the placement of the sun and stars and thus could be used to track the
hours as well as the seasons; but a staff is not a disk.
Thanks for any leads you can of
Hi Peter,
Thanks.
Yes, I'd seen that article but I'm not convinced by the its thesis -
that the object's main purpose is for finding latitude. They're saying
that the much-discussed curved line can trace a nodus' shadow by use of
a secondary gnomon placed off-centre. For me this does not ring
Hello everyone,
Some fellow has coloured a world map to show the difference between the
time zones and local solar time worldwide. See
http://poisson.phc.unipi.it/~maggiolo/index.php/2014/01/how-much-is-time-wrong-around-the-world/
Click the small map on the this blog to see the map in full s
On 09/05/2014 5:08 PM, Sunclocks North America wrote:
Also, I was wondering if anybody could tell me what are the typical
requirements for people to be allowed to use random copyrighted images
from the internet, and what my rights and possible recourses are in
such cases of the unauthorized use
.sunclocks.net>
On May 9, 2014, at 18:15, Steve Lelievre
<mailto:steve.lelievre.can...@gmail.com>> wrote:
On 09/05/2014 5:08 PM, Sunclocks North America wrote:
Also, I was wondering if anybody could tell me what are the typical
requirements for people to be allowed to use random
Hello, everyone,
A recent NASS Compendium included an article on the use of a Shepherd's
Dial as a compass. The author reported orientation errors in field use
of up to 25 degrees in the hour either side of noon but 5 degrees or
less in other parts of the day. This is consistent with my findin
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