SUNSTONE, SUN COMPASS
IE J
There have been many assumptions and ideas presented for the Viking
Sunstones and Sun Compasses. Scholars and other have arrived to conclusions
of all kind. These below are but a few of all those who presented their
thoughts for artifacts found.
http://www.etimage.com
http://www.sjolander.com/viking/essays/sunstone/psundial.htm
Looking at http://www.etimage.com's left upper picture you will find one of
the types which here and by some others are thought to be a sunstone. Well
that's a sun-clock for me nothing else. The presumed lines giving a 'map'
might be of interest or not, but it's certainly not a sunstone.
In http://www.sjolander.com/viking/essays/sunstone/psundial.htm Sjolander
presents a sundial. If you look at the three small photos where he describe
light's polarisation, you will find one type of tool in which a sunstone can
and could be placed.
A sunstone was placed on top of a piece of wood and as usual the Norse did
divide the sky in quarters. Thus the small piece of wood with a sunstone at
the top was placed in a 'brick' where there were small holes and a peg on a
rope which could be moved in order to measure the angle of the sunhight.
Essential to remember is that a sunstone is/was a small stone you can/could
hold it in your hand and if you do hold it you can depending on the material
use it in two different ways. Either you will be able to see through it when
hold up in direction of the sun, or you will see reflection from the
sunlight even if you are sailing in rain, storm and fog. Now I am most
familiar with the later type.
There were also an other astronomic instrument used here as well as in
Ancient Greece. Forgotten by many to have existed. I am talking of the
instrument that in it's later versions came to be called astrolabe. That was
a type of diopter. That type of astrolabe was described by Hipparchos
(190-125 BD) in other word an instrument known since ancient age. This
instrument consisted of two thin plates placed at same hight on a wooden
stick. The primitive variant used by the Vikings had plates made from what
we in Sweden call 'blände' http://runeberg.org/nfbc/0443.html
"Såsom sikte användes i äldre tider dioptern, sedermera tuberna. Dioptern
består af tvenne
skifvor, som äro fästade i hvardera ändan af en staf och som på exakt samma
höjd öfver underlaget ....."
quick translation: For sight in older/ancient ages diopter was used, later
came the tubes. A diopter has two plates/discs, who are fasten one in each
end of a stick and on the same hight over the base [stick].
http://runeberg.org/nfbb/0170.html
The viking age variant of a diopter was a primitive astrolabe but it served
it's mission especiall to measure the grades of the stars at night. Now the
'bländen' also could be used to establish in which direction the sun was at
any given moment. But as said a primitive instrument.
SUNCOMPASS
On this side http://runeberg.org/nfbb/0175.html those who can read Swedish
can read about a later instrument being used same way as the curve (the
shadow from sunlight) on the
suncompass moves around. The 'comb'-marks on the suncurve(on the suncompass
was read to measure important stars 'deklinationdivergence'.
A type of Suncompass you can see called 'Bearing-dial' to the left in
<http://www.etimage.com>
Please observe that the 'hacks' in the outher parts of the 'dial' has 18
hacks for a half circle. These represent each 10 degrees angle and the first
time I know that such was used was by Nicholas of Thingeyre (not the
Nicholas some assume him to have been. That is if you don't believe in a
person being known to have been in two different places, Iceland and Rome,
at same time and documented to have stayed in each places for a year!) in
1100's. I have no idea how old such a sun compass, because that's what it
is, can be.
When used as Sun compass for reading the time, which wasn't the same as
reading directions, one need to know how the days were measured in old age.
Up to the time of established Christianity in Scandinavian territories the
day and night was thought to be half of a day each no matter if the day was
shorter in our modern 'hours' than the night. A day was divided in quarters
and each quarter was divided in three parts.
Now a day even after Christian beliefs been introduced always was the day of
a farmer. Which during daily week was relatively close to the day in a
monastery. Of course there were monks who stood up as early as 03.00 in the
morning, but the ordinary day began at 05.00. Please remember that in those
days they didn't have a watch so the correct time could be +/- 30 minuites.
A day ended at 19.00 in the evening. This gives not twelve but 14 hours. I
will return to this later on.
Inger E
Peter Alaca
I don't believe you.
I believe Thorsteinn Vilhjalmsson
http://www.raunvis.hi.is/~thv/t_t.html
--
p.a.
Dylan Sung
"Peter Alaca" <P.A...@jul.nn> wrote in message
news:44a62892$0$62241$dbd4...@news.wanadoo.nl...
As papers goes, Vilhjalmsson's paper is well written, with salient points
from other authors acknowledged by hyperlink (otherwise superscript) to the
appropriate source in the endnotes which also serve as a clarification of
the point. As a piece of reading, it is methodical in its presentation. None
of Inger's bibliography dump without being pointed to the appropriate
supporting evidence to the points she makes, nor any of the unnamed scholars
business. Moreover, there's none of the here's something but I'll tell you
more later crap either.
To guage whether a piece is written in an unbiased way, two important words
to look out for "however" and "but". However occurs 14 times, but occurs 40
times in Vilhjalsson's piece. In Inger's writing above, she clocks up no
"however"'s and just 6 buts.
If Inger wants to write something worth reading, reading Thorsteinn
Vilhjalmsson's paper will show you the type of things she needs to be taken
anywhere near serious scholarship.
Dyl.
Peter Alaca
> "Peter Alaca" <P.A...@jul.nn> wrote in message
> news:44a62892$0$62241$dbd4...@news.wanadoo.nl...
>> IE J wrote: news:Hxppg.7009$E02....@newsb.telia.net
>>> [...]
>> I don't believe you.
>> I believe Thorsteinn Vilhjalmsson
>> http://www.raunvis.hi.is/~thv/t_t.html
> As papers goes, Vilhjalmsson's paper is well written, with salient
> points from other authors acknowledged by hyperlink (otherwise
> superscript) to the appropriate source in the endnotes which also
> serve as a clarification of the point. As a piece of reading, it is
> methodical in its presentation. None of Inger's bibliography dump
> without being pointed to the appropriate supporting evidence to the
> points she makes, nor any of the unnamed scholars business. Moreover,
> there's none of the here's something but I'll tell you more later
> crap either.
> To guage whether a piece is written in an unbiased way, two important
> words to look out for "however" and "but". However occurs 14 times,
> but occurs 40 times in Vilhjalsson's piece. In Inger's writing above,
> she clocks up no "however"'s and just 6 buts.
But her 'buts' are of the wrong kind
"These below are but a few of all those who
presented their thoughts for artifacts found."
"The presumed lines giving a 'map' might be of
interest or not, but it's certainly not a sunstone."
"a diopter was a primitive astrolabe but it served
it's mission especiall to measure the grades of
the stars at night"
"Now the 'bländen' also could be used to
establish in which direction the sun was at any
given moment. but as said a primitive instrument."
"Of course there were monks who stood up as
early as 03.00 in the morning, but the ordinary
day began at 05.00."
"This gives not twelve but 14 hours."
> If Inger wants to write something worth reading, reading Thorsteinn
> Vilhjalmsson's paper will show you the type of things she needs to be
> taken anywhere near serious scholarship.
--
p.a.
Eric Stevens
wrote:
>SUNSTONE, SUN COMPASS
>There have been many assumptions and ideas presented for the Viking
>Sunstones and Sun Compasses. Scholars and other have arrived to conclusions
>of all kind. These below are but a few of all those who presented their
>thoughts for artifacts found.
>
>http://www.etimage.com
>http://www.sjolander.com/viking/essays/sunstone/psundial.htm
>
>Looking at http://www.etimage.com's left upper picture you will find one of
>the types which here and by some others are thought to be a sunstone. Well
>that's a sun-clock for me nothing else. The presumed lines giving a 'map'
>might be of interest or not, but it's certainly not a sunstone.
Of course not. It's sun compass.
Eric Stevens
Eric Stevens
wrote:
Do you mean when he wrote:
"A well-known candidate for a Viking age navigational "instrument"
has been called a bearing-dial. It is a disk-shaped piece of wood
with a notched edge found in an excavation near Narsarsuaq in
Greenland in 1948.(22) The notches on the edge of the disk are
fairly regular although not overwhelmingly so. Some authors have
also wanted to lend significance to some scrapes on the surface of
the disk, which to other observers will look like incidental
scratches. For me it is quite conceivable that such a device might
have been used for time-keeping, e.g. at a farm. The peculiar
northern feature of the nearly horizontal motion of the sun
through the day as described above would have made this simple
device useful in certain circumstances, e.g. for people living at
a southern shore with no natural direction marks near the route of
the sun. This might also hold for people staying through the day
at a given place in otherwise unknown territory. But for people at
open sea it is not easy to see how such a rough device would add
decisive and significant information to what they would be able to
get without it."
If you do, all that I can see is expression of his inability to
understand what it is all about. I fail to see what there is in this
statement to justify 'belief' by anybody.
Eric Stevens
Peter Alaca
I fail to see what there is in your and Inger's statements
to justify 'belief' by anybody.
--
p.a.
IE J
"Eric Stevens" <eric.s...@sum.co.nz> wrote in message
news:65gca2tfm7f2o176d...@4ax.com...
Good points Eric. I forgot to say directly that I as a person neither
support one or the other of those behinds the two urls showing those
persons' beliefs. however I thought the lines I wrote made that clear that I
only presented two of the assumptions and conclusions presented on net in
the sunstone sun compass case.
Inger E
Inger E
>
>
>
> Eric Stevens
>
BernardZ
experienced people in sailing can learn to navigate across thousands of
miles of ocean by using stars, waves, and flight of birds to find their
way without any equipment.
The Vikings would not have needed someone as good as this person for
their navigation but here is the story of a man who decided to study
wayfinding under Mau Piailug, a master navigator from the island of
Satawal in Micronesia.
http://www.pbs.org/wayfinders/wayfinding2.html
http://www.pbs.org/wayfinders/wayfinding3.html
--
Self control is what keeps us from being rapist.
Observations of Bernard - No 100
##minty
BernardZ wrote:
>
>
> --
> Self control is what keeps us from being rapist.
>
> Observations of Bernard - No 100
For proper English, put s at the end of rapist. It complements "us" as
it is a plural pronoun.
##minty..
Eric Stevens
wrote:
>Actually I suspect that the Vikings might have used wayfinders. Very
>experienced people in sailing can learn to navigate across thousands of
>miles of ocean by using stars, waves, and flight of birds to find their
>way without any equipment.
>
>The Vikings would not have needed someone as good as this person for
>their navigation but here is the story of a man who decided to study
>wayfinding under Mau Piailug, a master navigator from the island of
>Satawal in Micronesia.
>
>http://www.pbs.org/wayfinders/wayfinding2.html
>
>http://www.pbs.org/wayfinders/wayfinding3.html
No doubt there were similarities in the respective navigational
techniques but the problems were somewhat different. Pacific islanders
had very many more islands to deal with and in most cases the islands
were smaller than those sought by the vikings. In most respects
finding one's way around the western parts of the Pacific was a far
more complex task than making the jumps from Hebrides, Faroes,
Iceland, Greenland and North America. On the other hand, many of the
voyages in the pacific were shorter than those which the Vikings had
to make.
The vikings were certainly in a situation where navigational knowledge
had to be aquired but it is most likely that it was aquired by
experience. No one person could live long enough to experience all the
possible voyages in the Pacific and it was for this reason that
Pacific islanders had to develop stick charts and memorise what they
meant. See http://tinyurl.com/g3tdc
Eric Stevens
Eric Stevens
wrote:
Belief has no place in science.
Eric Stevens
Peter Alaca
But Inger and you are expecting from us to
believe you on your word.
If belief is expected, then I prefer in this case
to believe Vilhjalmsson.
That has nothing to do with faith, but everything
with argumentation and trustworthy presentation.
I have to trust someone in matters in which I am
no expert myself, and that someone certainly is
not Inger.
--
p.a.
Dylan Sung
"Peter Alaca" <P.A...@jul.nn> wrote in message
>
> But Inger and you are expecting from us to
> believe you on your word.
> If belief is expected, then I prefer in this case
> to believe Vilhjalmsson.
> That has nothing to do with faith, but everything
> with argumentation and trustworthy presentation.
> I have to trust someone in matters in which I am
> no expert myself, and that someone certainly is
> not Inger.
Testable arguments presented with verifiable facts - that is science.
I think your 'belief' is more akin to "blind faith", which is for the ship
of fools. How many knots does that vessel travel at, and is it blown by a
howling gale, or set adrift like flotsom on the gluf stream current?
Goodnight! ;-)
Dyl.
Peter Alaca
BernardZ
> had to be aquired but it is most likely that it was aquired by
> experience. No one person could live long enough to experience all the
> possible voyages in the Pacific
The same could be said of the Vikings voyages.
Two different people with similar problems, its quite likely that they
come up with a similar solution. AT the very least its a *possible*
solution, I am proposing.
--
It is best to travel the path of life with some one else but its nice to
go alone for a short time.
Observations of Bernard - No 101
IE J
We had same for the streams and wave-collision between streams here in the
North Sea. It's long ago since the days when I sat down listning to the
Elderly who talked to my grandfather and my uncles about where to change
from one stream going north or west to the next in order to 'arrive' safely
where one intended.
Here along the coast in Sweden and Norway we have cairns to help us knowing
when to shift from a north to a south stream. The cairns are old and you
shall travel the sea out so you can see a specific number of cairns in
specified directions before you are to leave one stream and catch the next
one.
Inger E
>
>
>
> Eric Stevens
>
IE J
"BernardZ" <bern...@Nospam.com> wrote in message
news:MPG.1f11d339d1db31f5989a3a@news...
> > The vikings were certainly in a situation where navigational knowledge
> > had to be aquired but it is most likely that it was aquired by
> > experience. No one person could live long enough to experience all the
> > possible voyages in the Pacific
>
> The same could be said of the Vikings voyages.
>
> Two different people with similar problems, its quite likely that they
> come up with a similar solution. AT the very least its a *possible*
> solution, I am proposing.
very possible one.
Inger E
Peter Alaca
That is very helpfull when crossing the Atlantic.
--
p.a.
Eric Stevens
wrote:
>> The vikings were certainly in a situation where navigational knowledge
>> had to be aquired but it is most likely that it was aquired by
>> experience. No one person could live long enough to experience all the
>> possible voyages in the Pacific
>
>The same could be said of the Vikings voyages.
>
>Two different people with similar problems, its quite likely that they
>come up with a similar solution. AT the very least its a *possible*
>solution, I am proposing.
Certainly the approaches to navigation of the Pacific Islanders and
the Vikings would have had elements in common. But there were many
differences also. Getting sense out of a sun compass at or near the
equator would be difficult to put it mildly. :-)
However, getting back to the point, I am not aware that Vikings used
people formally trained as 'wayfinders'. I could be wrong and I am
interested to find out if that is the case.
Eric Stevens
Eric Stevens
wrote:
>Eric Stevens wrote: news:hvuda2tgovi7srq3j...@4ax.com
>
>> On Sat, 1 Jul 2006 11:58:12 +0200, "Peter Alaca" <P.A...@jul.nn>
>> wrote:
>>
>>> Eric Stevens wrote: news:65gca2tfm7f2o176d...@4ax.com
>>>
>>>> On Sat, 1 Jul 2006 09:46:44 +0200, "Peter Alaca" <P.A...@jul.nn>
>>>> wrote:
>>>>
--- snip ----
1. I do not speak for Inger.
2. I don't expect anyone to believe in anything I say except in the
sense that they accept that I am not trying to mislead them.
3. I am puzzled at what there is to believe in the quotation from
Vilhjalmsson unless you want to believe that he was not trying to
mislead you as to his opinion.
4. Vilhjalmsson does not seem to understand the principle of the sun
compass and seems to regard it as some kind of fancy sundial. It
puzzles me as to why he thinks farmers should need this device rather
than a sundial. If you accept Vilhjalmsson as being correct I would be
interested in your explanation of why a sundial would not do.
Eric Stevens
Peter Alaca
> "Peter Alaca" wrote:
>> Eric Stevens wrote:
>>> "Peter Alaca"wrote:
>>>> Eric Stevens wrote:
>>>>> "Peter Alaca" wrote:
> --- snip ----
I didn't say that and I don't think that.
> 2. I don't expect anyone to believe in anything I say except in the
> sense that they accept that I am not trying to mislead them.
I dindn't say that and I don't think you do.
> 3. I am puzzled at what there is to believe in the quotation from
> Vilhjalmsson unless you want to believe that he was not trying to
> mislead you as to his opinion.
>
> 4. Vilhjalmsson does not seem to understand the principle of the sun
> compass and seems to regard it as some kind of fancy sundial. It
> puzzles me as to why he thinks farmers should need this device rather
> than a sundial. If you accept Vilhjalmsson as being correct I would be
> interested in your explanation of why a sundial would not do.
If "Vilhjalmsson does not seem to understand ..."
is all you have to say, I stick to his opinion for
the time being.
--
p.a.
BernardZ
eric.s...@sum.co.nz says...
> However, getting back to the point, I am not aware that Vikings used
> people formally trained as 'wayfinders'.
They probably would not be *formally* trained as such. People would over
many trips share experiences with other sailors and learn about the
winds, the different types of waves, the ways of reading the sun and the
stars, the birds etc etc etc. In time, some of these people would have
a sense for knowing the way to go.
Note the same ability has been reported by people for some Arabs in the
deep desert.
> I could be wrong and I am
> interested to find out if that is the case.
>
So would I.
IE J
What might, but just might, be an indication for such a person or a
tradition told is the phrases telling of the birds being seen before they
changed course.
Now there are other things I learnt myself apart from birds and changes of
color in the horizon but that deals more or less with changing of color on
the sea when you came close to land, = when there were underwater vegetation
at distance or underwater skerries. So I have nothing but the small notes in
Icelandic Sagas and some of the Norwegian 'Kväde' to hint that this could be
the case.
Inger E
>
>
>
> Eric Stevens
>
Vaughan Sanders
"IE J" <inger_e....@telia.com> wrote in message
news:heQpg.7234$E02....@newsb.telia.net...
You three are making a good case for the northern route.
Which of natures indications would you use in the middle of the Atlantic on
a direct route from Bergen to Delaware for example?
Shallow banks cause the change in colour of the water and are the feeding
grounds of fish that attract the sea birds and other predators in the food
chain, where are they?
Jamie
IE J
"Vaughan Sanders" <v...@jamie-san.demon.co.uk> wrote in message
news:e88r83$rfs$1$8300...@news.demon.co.uk...
Most of those stories of the crossing I have read speaks of the soutern
route. But then those who aren't written 250-300 years AFTER the voyage were
later voyages from 1340 on forward.
Heading out from southern Norway westward passing the Shetlands and than
direct on.
> Shallow banks cause the change in colour of the water and are the feeding
> grounds of fish that attract the sea birds and other predators in the food
> chain, where are they?
According to those who sailed to Greenland they were close north of the
Shetland Island and south of where they first saw a change in distans that
indicated the high mountain/fjelds of Iceland soon to be seen.
Inger E
>
> Jamie
>
>
Vaughan Sanders
Well Faroes anyway, the marine life gave a clue to their position south of
Iceland, where are these reference points in the middle of the Atlantic?
Lat 61n is 160 miles south of Iceland, way out of sight of land.
Jamie
Eric Stevens
wrote:
---- snip -----
>> 4. Vilhjalmsson does not seem to understand the principle of the sun
>> compass and seems to regard it as some kind of fancy sundial. It
>> puzzles me as to why he thinks farmers should need this device rather
>> than a sundial. If you accept Vilhjalmsson as being correct I would be
>> interested in your explanation of why a sundial would not do.
>
>If "Vilhjalmsson does not seem to understand ..."
>is all you have to say, I stick to his opinion for
>the time being.
Then, seriously, why should farmers need the complications of a sun
compass rather than a sun dial when it comes to telling the time?
Eric Stevens
Peter Alaca
Eric Stevens
wrote:
>Eric Stevens wrote: news:kuaha219lu1g89ber...@4ax.com
>
>> On Sun, 2 Jul 2006 11:34:16 +0200, "Peter Alaca" <P.A...@jul.nn>
>> wrote:
>>
>> ---- snip -----
>>
>>>> 4. Vilhjalmsson does not seem to understand the principle of the
>>>> sun compass and seems to regard it as some kind of fancy sundial. It
>>>> puzzles me as to why he thinks farmers should need this device
>>>> rather than a sundial. If you accept Vilhjalmsson as being correct
>>>> I would be interested in your explanation of why a sundial would
>>>> not do.
>>>
>>> If "Vilhjalmsson does not seem to understand ..."
>>> is all you have to say, I stick to his opinion for
>>> the time being.
>>
>> Then, seriously, why should farmers need the complications of a sun
>> compass rather than a sun dial when it comes to telling the time?
>
>Because they had no cuckooclock.
... and in this you claim to believe. :-(
Eric Stevens
IE J
One can't always trust a cuckooclock....
Inger E
>
>
>
> Eric Stevens
>
Dylan Sung
Some sites for your perusal:
http://viking.sjolander.com:5150/wiki/index.php/Main_Page
http://viking.sjolander.com:5150/wiki/index.php/Considerations_on_The_Viking_Sun_Compass
http://www.sjolander.com/viking/essays/ideas.htm
http://www.sjolander.com/viking/3inch/9inch/watch.htm
http://www.wam.umd.edu/~eowyn/Longship/viking.nav.html
http://www.sciencebuddies.org/mentoring/project_ideas/Astro_p015.shtml?from=Home
http://www.griffithobs.org/IPS%20Planetarian/IPSViking.html
http://www.regia.org/Ships2.htm
http://www.robinknox-johnston.co.uk/da/20090
Dyl.
Eric Stevens
The above article concisely sets out the background to the sun
compass. http://members.aol.com/jvlambert/Norman/SunCompass.htm and
its links gives more information.
>
>http://www.sjolander.com/viking/essays/ideas.htm
>
>http://www.sjolander.com/viking/3inch/9inch/watch.htm
>
>http://www.wam.umd.edu/~eowyn/Longship/viking.nav.html
>
>http://www.sciencebuddies.org/mentoring/project_ideas/Astro_p015.shtml?from=Home
>
>http://www.griffithobs.org/IPS%20Planetarian/IPSViking.html
>
>http://www.regia.org/Ships2.htm
>
>http://www.robinknox-johnston.co.uk/da/20090
>
This last URL is new to me. In contrast to some of the others which
might be described as slightly nutty speculation it describes a
practical trial of the sun compass by an experienced deep water
sailor. It is clear that he found that it worked and he reported
accuracy which could only be easily improved upon by someone using
modern GPS technology. Most interesting - and thank you.
Eric Stevens
Peter Alaca
But it is clear that the use of a suncompass
is limited in time and space, and that it is
difficult to use on a ship.
--
p.a.
IE J
Yes Dylan needs credit for those url:s.
Didn't notice it until I opened the group and then you Eric was the latest
to write in the subject. Thus I also must add that I haven't heard of the
sun compass found in Poland. That I missed. I wonder if you two knows were
it was found?
Inger E
>
>
>
> Eric Stevens
>
jackli...@earthlink.net
Probably difficult to use on a camel too but better than what else was
available. The article suggests using two people, most ships have two
people on them for this purpose.
Peter Alaca
> Yes Dylan needs credit for those url:s.
> Didn't notice it until I opened the group and then you Eric was the
> latest to write in the subject. Thus I also must add that I haven't
> heard of the sun compass found in Poland. That I missed. I wonder if
> you two knows were it was found?
You missed that although it is no recent discovery.
Found in Wolin/Vineta. Dated first half 11th c.
But the identification as a sun compass is not certain.
It is kept at the Instytut Archeologii i Etnologii Polskiej
Akademii Nauk in Wolin.
--
p.a.
IE J
<jackli...@earthlink.net> wrote in message
news:1151964562.3...@v61g2000cwv.googlegroups.com...
Apart from which it didn't need more than one person to use a sun compass.
Inger E
>
Peter Alaca
On a small ship in the middle of the ocean not
even ten men are enough to keep the thing level.
--
p.a.
IEJ
"Peter Alaca" <P.A...@jul.nn> wrote in message
that hadn't been a problem. BUT a small ship?????
The smallest ship noted to have been sailed by Norse in Greenlandic NA
waters Thorhall who had nine men in his party. Nothing indicating a small
ship. Not necessarily a major transport ship, but probably more like the
later, since his as well as Karlsfni's and Biarni's ship had livestock on
board....
Inger E
>
>
Dylan Sung
"Peter Alaca" <P.A...@jul.nn> wrote in message
news:44a9a0a9$0$13405$dbd4...@news.wanadoo.nl...
"In the far northern latitudes, where even a magnetic compass is often
unreliable, the direction of the sun can be more trustworthy. But direction
is also vital in storm, fog and under overcast skies - precisely when ships
get into trouble. In the Icelandic Flateyjarbok, the Saga of St. Olaf
describes a "Solarsteinn" or sunstone, by which mariners claimed to be able
to tell the direction of the sun when it was obscured by cloud or fog.
Some Viking experts, like William Fitzhugh at the Smithsonian, dispute the
sunstone claim, but others believe it was Icelandic spar, the dichroic
mineral cordierite. It is a transparent form of calcite and natural light
passing through it is double refracted, so that even through cloud or fog, a
sun image can be projected. The principle, rediscovered during World War II,
was used to make a polariscope to help aerial navigators find their way when
magnetic compasses failed on transpolar flights."
http://www.shipsonstamps.org/topics/html/kompass.htm
Interesting stamp collection with one depicting a sun compass and IR-Land.
Those things must be huge! ;-)
http://www.rscds-canberra.org/texts/The%20quest%20for%20Pelorus%20web.pdf
Pelorus, mounted on gimbals. "the vikings used something like it"
I wonder if they had gimbals - the Vikings I mean. That would keep the thing
steady, but from the picture in the links and the postage stamp, it looks to
be a hand held device. Do any have 'sights' like the mounted pelorus?
Dyl.
Peter Alaca
> "Peter Alaca"wrote
>> IE J wrote:
>>> <jacklinthicum wrote
>>>> Peter Alaca wrote:
>>>>> Eric Stevens wrote:
>>>>>>> Some sites for your perusal:
>>>>>>> http://viking.sjolander.com:5150/wiki/index.php/Main_Page
>>>>>>> http://viking.sjolander.com:5150/wiki/index.php/Considerations_on_The_Viking_Sun_Compass
>>>>>> The above article concisely sets out the background to the sun
>>>>>> compass. http://members.aol.com/jvlambert/Norman/SunCompass.htm
>>>>>> and its links gives more information.
>>>>>>> http://www.sjolander.com/viking/essays/ideas.htm
>>>>>>> http://www.sjolander.com/viking/3inch/9inch/watch.htm
>>>>>>> http://www.wam.umd.edu/~eowyn/Longship/viking.nav.html
>>>>>>> http://www.sciencebuddies.org/mentoring/project_ideas/Astro_p015.shtml?from=Home
>>>>>>> http://www.griffithobs.org/IPS%20Planetarian/IPSViking.html
>>>>>>> http://www.regia.org/Ships2.htm
>>>>>>> http://www.robinknox-johnston.co.uk/da/20090
>>>>>> This last URL is new to me. In contrast to some of the others
>>>>>> which might be described as slightly nutty speculation it
>>>>>> describes a practical trial of the sun compass by an experienced
>>>>>> deep water sailor. It is clear that he found that it worked and
>>>>>> he reported accuracy which could only be easily improved upon by
>>>>>> someone using modern GPS technology. Most interesting - and
>>>>>> thank you.
>>>>> But it is clear that the use of a suncompass
>>>>> is limited in time and space, and that it is
>>>>> difficult to use on a ship.
>>>> Probably difficult to use on a camel too but better than what else
>>>> was available. The article suggests using two people, most ships
>>>> have two people on them for this purpose.
>>> Apart from which it didn't need more than one person to use a sun
>>> compass.
>> On a small ship in the middle of the ocean not
>> even ten men are enough to keep the thing level.
> that hadn't been a problem. BUT a small ship?????
> The smallest ship noted to have been sailed by Norse in Greenlandic NA
> waters Thorhall who had nine men in his party. Nothing indicating a
> small ship. Not necessarily a major transport ship, but probably more
> like the later, since his as well as Karlsfni's and Biarni's ship had
> livestock on board....
Ten men is no indication for a large ship.
But that is not the point. Even a large ship is
difficult to keep stable.
For a sun-compass you need an open sky
and a very calm sea. And a sun-compass must
be made for the correct time and place.
Of course everything is better than nothing, but
I don't think there were many opportunities to
use a sun-compass at sea. If you can see the
sun, you don't need a sun-compass to know
in which direction to go and if you can't see the
sun there is no use for a sun-compass.
--
p.a.
Peter Alaca
> "Peter Alaca" <P.A...@jul.nn> wrote in message
>> On a small ship in the middle of the ocean not
>> even ten men are enough to keep the thing level.
>>
> http://www.bayjournal.com/article.cfm?article=739
> "In the far northern latitudes, where even a magnetic compass is often
> unreliable, the direction of the sun can be more trustworthy. But
> direction is also vital in storm, fog and under overcast skies -
> precisely when ships get into trouble. In the Icelandic Flateyjarbok,
> the Saga of St. Olaf describes a "Solarsteinn" or sunstone, by which
> mariners claimed to be able to tell the direction of the sun when it
> was obscured by cloud or fog. Some Viking experts, like William
> Fitzhugh at the Smithsonian,
> dispute the sunstone claim, but others believe it was Icelandic spar,
> the dichroic mineral cordierite. It is a transparent form of calcite
> and natural light passing through it is double refracted, so that
> even through cloud or fog, a sun image can be projected. The
> principle, rediscovered during World War II, was used to make a
> polariscope to help aerial navigators find their way when magnetic
> compasses failed on transpolar flights."
The polarization of the sunlight can't be used
behind thick clouds.
> http://www.shipsonstamps.org/topics/html/kompass.htm
> Interesting stamp collection with one depicting a sun compass and
> IR-Land. Those things must be huge! ;-)
>
> http://www.rscds-canberra.org/texts/The%20quest%20for%20Pelorus%20web.pdf
> Pelorus, mounted on gimbals. "the vikings used something like it"
>
> I wonder if they had gimbals - the Vikings I mean. That would keep
> the thing steady, but from the picture in the links and the postage
> stamp, it looks to be a hand held device. Do any have 'sights' like
> the mounted pelorus?
Only minutes ago I was wondering how such a
compass mount is called. I was thinking of
gyroscope, but it is a gimbal.
--
p.a.
Leo Schmit
After a five week period of absence to SHM and just wading through the usual
barrage of off-topic postings, I stumble on this interesting subject, which
in anthropology would be discussed in terms of etnoscience or traditional
knowledge systems.
One point on the comparison of pre-scientific North-Atlantic and Pacific
navigation: Although valid their is a difference, while the Norsemen
travelled in boats with crews of between 20 to say 50 (?) persons, while the
Micronesians generally travelled in out-riggers with 2 to 6 individuals. (I
think only the Maori are known for their large barges). The chance for
having a specialised way-finder position in Nordic crews is thus bigger,
although I would assume this would be the captain. (Bergson, - Long Ships,
however suggests that captains were primarily acknowledged for their skills
in winning plenty of booty).
Concerning the smaller size of Micronesian vessels, this means that in fact
all Micronesians had to have navigation skills to survive their journeys.
I agree with the point on the aquisition of such knowledge and skills by
experience rather than 'formal' training. This, in the same way that
experienced captains of fishing boats add their intiuitive skills to their
electronic equipment to locate the fish.
As for the Pacific, their is a nice anthropological study by Thomas Gladwin
"East is is big bird" (1980 or around that year). As the title suggets
birds are important observables to find the way, but also currents, sun and
stars. Gladwin also deals with the question how master wayfairers transfer
their skills to apprentices by using sand models on the beach.
He also has an interesting note on how delivery truck drivers and
taxidrivers in New York use their navigation skills to get around in the
city.
Best,
Leo
"Peter Alaca" <P.A...@jul.nn> wrote in message
news:44a77f83$0$82478$dbd4...@news.wanadoo.nl...
Leo Schmit
(1970, Harvard University Press.)
Chapter 4 deals entirely with the subject of navigation and transferring
navigation skills (on sea and on the beach).
Reciting the star positions for all 28 islands (approach and departure
positions) is a major part of the instructions.
My assumption that all youths would take part in instructions is wrong. It's
a highly selective affair, according to Gladwin, with many drop-outs even
among the selected.
Apparently limited skills are sufficient to navigate the dense Caroline
Islands of which Puluwat is part.
For the long journey's Gladwin describes the navigation system as a 'dead
reckoning system' which means that "one's position at any time is
determined solely on the basis of distance and direction travelled since
leaving the last known location." "If you loose track of how long you have
come from where you were you are lost".
I wonder how this compares with the skills applied by the Northern
seafarers.
Simon Pugh
<eric.s...@sum.co.nz> writes
<snip>
>>http://www.robinknox-johnston.co.uk/da/20090
>>
>
>This last URL is new to me. In contrast to some of the others which
>might be described as slightly nutty speculation it describes a
>practical trial of the sun compass by an experienced deep water
>sailor. It is clear that he found that it worked and he reported
>accuracy which could only be easily improved upon by someone using
>modern GPS technology. Most interesting - and thank you.
>
>
>
>Eric Stevens
>
I wonder if the last URL is a little optimistic about the accuracy of
the sun compass. http://www.robinknox-johnston.co.uk/da/20090
The article talks about an accuracy one mile in 50 being achievable. A 1
nautical mile error in 60 nautical miles represents an accuracy of 1
degree IIRC. This is good going with a modern magnetic compass.
Can this really be achieved with a sun compass particularly at northern
latitudes? - the following table shows shadow length in the middle part
of the day 4 July in Iceland.
Hrs Az deg Shadow length cm with 1 cm pin.
11 114 1.37638192
12 130 1.110612515
13 149 0.965688775
14 169 0.900404044
15 190 0.900404044
16 220 0.965688775
17 228 1.110612515
18 245 1.37638192
It looks as though it is impossible to get an accurate north in the
middle of the day. It is better further south.
--
Simon Pugh
Remove X for mail
BernardZ
> For the long journey's Gladwin describes the navigation system as a 'dead
> reckoning system' which means that "one's position at any time is
> determined solely on the basis of distance and direction travelled since
> leaving the last known location." "If you loose track of how long you have
> come from where you were you are lost".
>
If I have a star, then I have a latitude. I don't need to know my
position unless I go too far and miss the Island altogether.
Eric Stevens
wrote:
Which no doubt is why Vilhjalmsson is prepared to believe it was used
by farmers but not by sailors. :-)
Any of the early compasses were difficult to use on a ship but I agree
the sun compass would be even more difficult. Nevertheless it is
possible as Robin Knox-Johnston has demonstrated.
Eric Stevens
Eric Stevens
wrote:
If your argument was correct it would not be possible to use an
astrolabe, a cross-staff, an octant, a sextant or any other
navigational device which requires that it be held level and steady in
use.
Eric Stevens
Peter Alaca
> "Peter Alaca" wrote:
>> IE J wrote:
>>> <jacklinthicum wrote
>>>>> Eric Stevens wrote:
>>>>>> <dylanwhs....@pacific.net.hk> wrote:
>>>>>>> [...]
>>>>>>> http://www.robinknox-johnston.co.uk/da/20090
>>>>>> This last URL is new to me. In contrast to some of the others
>>>>>> which might be described as slightly nutty speculation it
>>>>>> describes a practical trial of the sun compass by an experienced
>>>>>> deep water sailor. It is clear that he found that it worked and
>>>>>> he reported accuracy which could only be easily improved upon by
>>>>>> someone using modern GPS technology. Most interesting - and
>>>>>> thank you.
>>>>> But it is clear that the use of a suncompass
>>>>> is limited in time and space, and that it is
>>>>> difficult to use on a ship.
>>>> Probably difficult to use on a camel too but better than what else
>>>> was available. The article suggests using two people, most ships
>>>> have two people on them for this purpose.
>>> Apart from which it didn't need more than one person to use a sun
>>> compass.
>> On a small ship in the middle of the ocean not
>> even ten men are enough to keep the thing level.
> If your argument was correct it would not be possible to use an
> astrolabe, a cross-staff, an octant, a sextant or any other
> navigational device which requires that it be held level and steady in
> use.
It seems you have a point, but my strong impression
is that a sun-compass is far less easy to handle than
the other instruments.
Imagine two men trying to stabilize such a small
device to get a 2 mm or less reading (see Simon's table).
--
p.a.
Vaughan Sanders
Going blind from looking directly at the sun was a major problem with a
cross-staff, particularly in northern latitudes with almost constant
daylight, the back-staff solved this problem.
http://www.mat.uc.pt/~helios/Mestre/Novemb00/H61iflan.htm
The sun compass can be used to just determine latitude.
Floating one in a pale of water would stabilize it in most sailing
conditions, the noon discrepancy during the short sailing season is +/- half
a degree of latitude apparently.
I used a pale of water to watch the last eclipse to protect my eyes.
The half disc found in Greenland having a huge hole for the gnomon would
need explaining however
http://viking.sjolander.com:5150/wiki/index.php/Considerations_on_The_Viking_Sun_Compass..
Is there a picture of the Polish sun compass on the net?
Jamie.
jackli...@earthlink.net
> >
> > "Vaughan Sanders" <v...@jamie-san.demon.co.uk> wrote in message
> > news:e88r83$rfs$1$8300...@news.demon.co.uk...> >> news:heQpg.7234$E02....@newsb.telia.net...> >> > news:e7mea2td1bh4dhpim...@4ax.com...
> >> >> On Sun, 2 Jul 2006 11:58:10 +1000, BernardZ <bern...@Nospam.com>
> >> >> wrote:
> >> >>
> >> >> >> The vikings were certainly in a situation where navigational
> > knowledge
> >> >> >> had to be aquired but it is most likely that it was aquired by
> >> >> >> experience. No one person could live long enough to experience all
> > the
> >> >> >> possible voyages in the Pacific
> >> >> >
> >> >> >
> >> >> >Two different people with similar problems, its quite likely that
> >> >> >they
> >> >> >come up with a similar solution. AT the very least its a *possible*
> >> >> >solution, I am proposing.
> >> >>
> >> >> Certainly the approaches to navigation of the Pacific Islanders and
> >> >> the Vikings would have had elements in common. But there were many
> >> >> differences also. Getting sense out of a sun compass at or near the
> >> >> equator would be difficult to put it mildly. :-)
> >> >>
> >> >> However, getting back to the point, I am not aware that Vikings used
> >> >> people formally trained as 'wayfinders'. I could be wrong and I am
> >> >> interested to find out if that is the case.
> >> >
> >> > What might, but just might, be an indication for such a person or a
> >> > tradition told is the phrases telling of the birds being seen before
> > they
> >> > changed course.
> >> >
> >> > Now there are other things I learnt myself apart from birds and changes
> > of
> >> > color in the horizon but that deals more or less with changing of color
> > on
> >> > the sea when you came close to land, = when there were underwater
> >> > vegetation
> >> > at distance or underwater skerries. So I have nothing but the small
> > notes
> >> > in
> >> > Icelandic Sagas and some of the Norwegian 'Kväde' to hint that this
> > could
> >> > be
> >> > the case.
> >> >
> >> > Inger E
> >> >>
> >> >>
> >> >>
> >> >> Eric Stevens
> >> >>
> >> >
> >> >
> >>
> >> You three are making a good case for the northern route.
> >> Which of natures indications would you use in the middle of the Atlantic
> > on
> >> a direct route from Bergen to Delaware for example?
> >
> > Most of those stories of the crossing I have read speaks of the soutern
> > route. But then those who aren't written 250-300 years AFTER the voyage
> > were
> > later voyages from 1340 on forward.
> > Heading out from southern Norway westward passing the Shetlands and than
> > direct on.
> >
> >
> >> Shallow banks cause the change in colour of the water and are the feeding
> >> grounds of fish that attract the sea birds and other predators in the
> >> food
> >> chain, where are they?
> >
> > According to those who sailed to Greenland they were close north of the
> > Shetland Island and south of where they first saw a change in distans that
> > indicated the high mountain/fjelds of Iceland soon to be seen.
> >
> > Inger E
> >>
>
> Well Faroes anyway, the marine life gave a clue to their position south of
> Iceland, where are these reference points in the middle of the Atlantic?
> Lat 61n is 160 miles south of Iceland, way out of sight of land.
>
> Jamie
Birds, clouds
ken...@cix.compulink.co.uk
(BernardZ) wrote:
> If I have a star, then I have a latitude. I don't need to know
> my position unless I go too far and miss the Island
> altogether.
Losing track of longitude on ocean crossings could be fatal. Sir
Cloudsley Shovel <sp> managed to lose his life and a large part
of his fleet because of an error in longitude. Anson lost a large
part of his crew to scurvy because he got longitude wrong and
thus delayed land fall. Dampnier give accounts of where he ended
up on the wrong side of an island and was unable to beat back
against prevailing winds. He also makes the point that the
limiting factor on long voyages was scurvy.
Ken Young
Peter Alaca
> "Eric Stevens" wrote
>> "Peter Alaca" wrote:
>>> But it is clear that the use of a suncompass
>>> is limited in time and space, and that it is
>>> difficult to use on a ship.
>>
>> Which no doubt is why Vilhjalmsson is prepared to believe it was
>> used by farmers but not by sailors. :-)
>>
>> Any of the early compasses were difficult to use on a ship but I
>> agree the sun compass would be even more difficult. Nevertheless it
>> is possible as Robin Knox-Johnston has demonstrated.
>>
>>
>>
>> Eric Stevens
>>
>
> Going blind from looking directly at the sun was a major problem with
> a cross-staff, particularly in northern latitudes with almost constant
> daylight, the back-staff solved this problem.
> http://www.mat.uc.pt/~helios/Mestre/Novemb00/H61iflan.htm
> The sun compass can be used to just determine latitude.
> Floating one in a pale of water would stabilize it in most sailing
> conditions,
That is a good solution, except for the horizontal positioning.
> the noon discrepancy during the short sailing season is
> +/- half a degree of latitude apparently.
> I used a pale of water to watch the last eclipse to protect my eyes.
>
> The half disc found in Greenland having a huge hole for the gnomon
> would need explaining however.
Good question.
Is the shadow of a thick (tapering?) gnomon
better visible in slightly overcast conditions?
> http://viking.sjolander.com:5150/wiki/index.php/Considerations_on_The_Viking_Sun_Compass..
>
> Is there a picture of the Polish sun compass on the net?
I didn't find one.
--
p.a.
Lech
wiadomości $8300...@news.demon.co.uk...
Yes it is:
http://www.wolin.pl/informator/listopad/wiesci.html
http://www.zsee.bytom.pl/sciaga/przygotowanie.pdf
Lech
<<Nie chwal dnia przed zachodem slonca>>
BernardZ
ken...@cix.compulink.co.uk says...
> In article <MPG.1f1531aa7586e43a989a4d@news>, bern...@Nospam.com
> (BernardZ) wrote:
>
(a)
> > If I have a star, then I have a latitude. I don't need to know
> > my position unless I go too far and miss the Island
> > altogether.
>
> Losing track of longitude on ocean crossings could be fatal. Sir
> Cloudsley Shovel <sp> managed to lose his life and a large part
> of his fleet because of an error in longitude. Anson lost a large
> part of his crew to scurvy because he got longitude wrong and
> thus delayed land fall. Dampnier give accounts of where he ended
> up on the wrong side of an island and was unable to beat back
> against prevailing winds. He also makes the point that the
> limiting factor on long voyages was scurvy.
>
> Ken Young
>
Mmmmmmmmmmmmmm
Ken yet again you display a bad habit of jumping in without reading what
people are saying. I have noticed it a lot.
Okay you have missed the point but interestingly your answer confirms
what I said.
Lets get back to the topic. Firstly read what I wrote at (a). Digest it.
Now say you leave Norway and go to Iceland.
You look for the star, find it and set course for the star. So you go
towards the correct latitude. Once there you stay at that latitude.
Somewhere on the way, you get lost eg a storm drives you off course.
As before you look for the star, find it and set course for the star. So
you go towards the correct latitude. Again once there you stay at that
latitude.
We have two possibilities
1) You are between Norway and Iceland so it does not matter as you are
going on the correct Latitude and will soon hit Iceland.
2) You have gone past Iceland, in which case like your Dampnier example
above, you are in real trouble.
--
It is best to travel the path of life with some one else but its nice to
go alone for a short time.
Observations of Bernard - No 101
IE J
On the contrary a sun compass is very very easy to be used by one single
person compared with a more advanced tool such as an astrolab. It takes less
then 2 minuites to place it in 'correct' position. You needn't have any
problem what so ever to hold it in your hand and hold it in a horisontal
position at start. What you need is to establish where south is and that
takes less than a minuite to do if you have brought a sunstone or a piece of
any stone that reflect light. then you place the sun compass so the mid part
points southward. Less than one minuite it takes to read the difference
between south and where your boat/ship is heading. Compare that with the
wanted direction and than you done what it takes.
Inger E
>
>
>
> Eric Stevens
>
IE J
Sorry Jamie it didn't take more than a half disc.
Inger E
>
>
Vaughan Sanders
"Lech" <le...@nospam.pl> wrote in message news:e8g6vs$34g$1...@nntp.aioe.org...
> Użytkownik "Vaughan Sanders" <v...@jamie-san.demon.co.uk> napisał w
> wiadomości $8300...@news.demon.co.uk...
>> >
>>
>> Going blind from looking directly at the sun was a major problem with
> a
>> cross-staff, particularly in northern latitudes with almost constant
>> daylight, the back-staff solved this problem.
>> http://www.mat.uc.pt/~helios/Mestre/Novemb00/H61iflan.htm
>> The sun compass can be used to just determine latitude.
>> Floating one in a pale of water would stabilize it in most sailing
>> conditions, the noon discrepancy during the short sailing season is
> +/- half
>> a degree of latitude apparently.
>> I used a pale of water to watch the last eclipse to protect my eyes.
>>
>> The half disc found in Greenland having a huge hole for the gnomon
> would
>> need explaining however
>>
> http://viking.sjolander.com:5150/wiki/index.php/Considerations_on_The_Viking_Sun_Compass..
>>
>> Is there a picture of the Polish sun compass on the net?
>
>
> Yes it is:
>
> http://www.wolin.pl/informator/listopad/wiesci.html
> http://www.zsee.bytom.pl/sciaga/przygotowanie.pdf
>
> Lech
>
> <<Nie chwal dnia przed zachodem slonca>>
>
Thanks.
There doesn't appear to be a gnomon curve for it to be used as a compass,
this appears to make the Knox-Johnson comments meaningless.
("In practice a perfectly satisfactory curve can be drawn from marks made at
hourly intervals. You have now created a simple sun compass")
http://members.aol.com/jvlambert/Norman/SunCompass.htm
The two circles could however cover the deviation of latitude either side of
summer solstice on lat 60 / 61 north.
This site claims the Greenland dial is complete
http://etimage.com/english/Medd14/solkompas/solkompas.htm
Jamie.
Vaughan Sanders
So explain the Polish disc, Jomsborg toy wagon wheel do you think :-))
Jamie
Peter Alaca
> "Vaughan Sanders" napisa
>> Is there a picture of the Polish sun compass on the net?
>
>
> Yes it is:
>
> http://www.wolin.pl/informator/listopad/wiesci.html
> http://www.zsee.bytom.pl/sciaga/przygotowanie.pdf
Thanks. It is quite different from the Greenland dial.
btw. see also http://tinyurl.com/hm2p7
--
p.a.
Peter Alaca
> "Vaughan Sanders" wrote
>> [...]
>> The half disc found in Greenland having a huge hole for the gnomon
>> would need explaining however
>> [...]
> Sorry Jamie it didn't take more than a half disc.
Sure Inger. That's why the Greenland disk is more
than a half and the Wolin disk is a full disc.
--
p.a.
IE J
How about understanding one thing:
A Sun Compass can but mustn't have a gnomen.
It can be used as easily without as with.
Anyhow one doesn't have to have a sun compass, for most purpose on see you
only have to know what a 90 degree angle is. When you established where
south is, everything else is easy.
Might be that BernhardZ is correct in his assumption re. wayfinders. No
matter which I would have thought that everyone had been taught how to use
what you got with you every where you go in order to find sailing
directions. All you need when establishing where south is is your own arms.
I was taught how to navigate on land as well as on sea only using those as
'tools' That's easy. If you happen to have a sun compass, which you and the
other missed always has 180 degrees marked as 18 hacks for 10 degrees each
on a half disc or half of the full disc, then you have an easy task to
establish much easier than dividing the 90 degree angle in three which you
can and people did in old days by making marks on the ship side.
Inger E
Vaughan Sanders
snip
>> >But it is clear that the use of a suncompass
>> >is limited in time and space, and that it is
>> >difficult to use on a ship.
>>
>> Which no doubt is why Vilhjalmsson is prepared to believe it was used
>> by farmers but not by sailors. :-)
>>
>> Any of the early compasses were difficult to use on a ship but I agree
>> the sun compass would be even more difficult. Nevertheless it is
>> possible as Robin Knox-Johnston has demonstrated.
>
> On the contrary a sun compass is very very easy to be used by one single
> person compared with a more advanced tool such as an astrolab. It takes
> less
> then 2 minuites to place it in 'correct' position. You needn't have any
> problem what so ever to hold it in your hand and hold it in a horisontal
> position at start. What you need is to establish where south is and that
> takes less than a minuite to do if you have brought a sunstone or a piece
> of
> any stone that reflect light. then you place the sun compass so the mid
> part
> points southward. Less than one minuite it takes to read the difference
> between south and where your boat/ship is heading. Compare that with the
> wanted direction and than you done what it takes.
>
> Inger E
>>
Is that due south or anywhere south, Inger?
Presumably if you needed a sunstone because of poor visibility you would not
be able to see the horizon, how would you level the compass or does that not
matter?
Jamie
Peter Alaca
> Vaughan,
> How about understanding one thing:
> A Sun Compass can but mustn't have a gnomen.
> It can be used as easily without as with.
?????
> Anyhow one doesn't have to have a sun compass, for most purpose on
> see you only have to know what a 90 degree angle is. When you
> established where south is, everything else is easy.
And how do you know where south is?
> Might be that BernhardZ is correct in his assumption re. wayfinders.
> No matter which I would have thought that everyone had been taught
> how to use what you got with you every where you go in order to find
> sailing directions. All you need when establishing where south is is
> your own arms. I was taught how to navigate on land
From home to kindergarten?
> as well as on sea
> only using those as 'tools' That's easy. If you happen to have a sun
> compass, which you and the other missed always has 180 degrees marked
> as 18 hacks for 10 degrees each on a half disc or half of the full
> disc, then you have an easy task to establish much easier than
> dividing the 90 degree angle in three which you can and people did in
> old days by making marks on the ship side.
>
> Inger E
the inventor of the gnomon-less sundial.
--
p.a.
Dylan Sung
"Peter Alaca" <P.A...@jul.nn> wrote in message
Ingenious with emphasis on the Ing.
Dyl.
Vaughan Sanders
> Vaughan,
> How about understanding one thing:
> A Sun Compass can but mustn't have a gnomen.
> It can be used as easily without as with.
>
> Anyhow one doesn't have to have a sun compass, for most purpose on see you
> only have to know what a 90 degree angle is. When you established where
> south is, everything else is easy.
Yep, if you know were south is and the wind is coming from that direction,
90 degree port tack will take you to NA, starboard tack Europe.
Problems only arise if you can't see the sun and have no reference to where
it should be.
>
> Might be that BernhardZ is correct in his assumption re. wayfinders. No
> matter which I would have thought that everyone had been taught how to use
> what you got with you every where you go in order to find sailing
> directions. All you need when establishing where south is is your own
> arms.
> I was taught how to navigate on land as well as on sea only using those as
> 'tools' That's easy.
Yep Inger I can navigate with my arms, if the sun is behind me and my right
arm is forward I know I'm sailing east, clever or what :-))
Sailing south in the winter I often need sunglasses as the sun is virtually
on the water..
>If you happen to have a sun compass, which you and the
> other missed always has 180 degrees marked as 18 hacks for 10 degrees each
> on a half disc or half of the full disc, then you have an easy task to
> establish much easier than dividing the 90 degree angle in three which you
> can and people did in old days by making marks on the ship side.
>
> Inger E
Seems a resonable way to divide 180, half the hack would give the 45 (north
west for example), what did I miss?
Jamie
JerryT
"Peter Alaca" <P.A...@jul.nn> skrev i meddelandet
news:44abba9e$0$52595$dbd4...@news.wanadoo.nl...
Some old thoughts.
http://www.columbusnavigation.com/vdisk.shtml
JT
> --
> p.a.
>
>
>
Peter Alaca
Thanks Jerry, very good. A must read.
Although I am only halfway the c 44 pages,
I am impressed. That's how I like it.
--
p.a.
IE J
Jamie,
ARE you telling me that non of your Elderly taught you how you should act in
order to find direct south and direct north if you so happen to be in an
open field or out at sea???????? Never thought that possible at all. THAT
was and is elementary knowledge we in my family have learnt when we where
children. Mind you my mother and my daughter do have problems like those you
describe. But then they have problems finding their way in an unknown part
of a city as well.
I never had that problem. Always known which direction I go/went etc. No
matter how many times I change direction I know where I am. But as I said I
know those who don't.
for me south is south and I can stand up on a mountain showing you where
south-south west is if you ask me.
Simple. Elementary knowledge.
Inger E
>
>
IE J
First of all: Anyone who doesn't protect his or her eyes in broad daylight
at see in sommer as well as in winter, had caused his/her own problem.
Secondly I can't understand why you have so much problem with knowing where
south is. No problem at all. That's the easy part. AND I mean direct south.
>
>
>
> >If you happen to have a sun compass, which you and the
> > other missed always has 180 degrees marked as 18 hacks for 10 degrees
each
> > on a half disc or half of the full disc, then you have an easy task to
> > establish much easier than dividing the 90 degree angle in three which
you
> > can and people did in old days by making marks on the ship side.
> >
> > Inger E
>
> Seems a resonable way to divide 180, half the hack would give the 45
(north
> west for example), what did I miss?
Yes you do. But then again you doesn't seem to understand the sun compass at
all. Go back to 4th grades measuring with the half circle where 0 - 180
degrees marked. You do exactly the same with the sun compass as you did when
your teacher showed you how to measure angles. No problem.
Inger E
>
> Jamie
>
>
Erik Hammerstad
Very nice, and so much in contrast to those who here who have so
strong opinions that the Greenland half-circle is a sun compass.
And to add to the uncertainty of the sun compass theory, at the
Vinland Millenium Symposium (2000) two professors in Nordic
Archaeology (Keller and Christensen) discussed an alternative
possibility, that the disk was a "confession disk" (a help for
priests in keeping count in the dark). As support for this theory
they note that the disk was found in the ruins of a probable
Benedictine convent, and that Vebćk (the finder) in a later
publication (1991) notes the uncertainty with regard to the dating
due to an unnoticed stratigraphy during the excavation so that the
disk is far from certainly a 11th century object (it must be later
to be a confession disk).
Additionally the two note the far from accurate carving of the
triangles on the disk, with a spacing varying from 4 to 9 mm with
a probable total of 35 if the disk originally was a full circle
(note than everybody excepting IEJ seems to agree that a medieval
compass should have 32). Thus the disk is not made with the
precision one should expect if it was intended to be used as a
navigational instrument.
At the symposium Carl Roslund together with Thirslund and Páztor
presented a paper on Viking Navigation. They mention the Greenland
disk and note a rather poorly carved gnomon-like curve on it, but
they really just raise the possibility that it is a sun compass.
Both papers are published in "Vinland Revisited", ed. Shannon
Lewis-Simpson, ISBN 0-919735-07-X. To connect the book to previous
discussions on sa, it also has Alan Crozier's Vinland paper, and
in its list of contributors confers the title Dr. to Birgitta Wallace.
Eric Stevens
wrote:
>Eric Stevens wrote: news:h4pla21ja934gp23m...@4ax.com
I think Simon's table was intended to be read as a series of ratios.
All the illustrations I have seen of sun compasses suggest that the
length of the shadow will be measured in centimetres - possibly 4 or
5cm.
Eric Stevens
Peter Alaca
Not the length is important bit the difference.
--
p.a.
Peter Alaca
But as far as I have read Enterline's "White paper",
the attribution to the site of the convent is not sure.
And if it is from that site, it is probably from beneath
the convent in disturbed ground.
>
> Additionally the two note the far from accurate carving of the
> triangles on the disk, with a spacing varying from 4 to 9 mm with
> a probable total of 35 if the disk originally was a full circle
> (note than everybody excepting IEJ seems to agree that a medieval
> compass should have 32). Thus the disk is not made with the
> precision one should expect if it was intended to be used as a
> navigational instrument.
>
> At the symposium Carl Roslund together with Thirslund and Páztor
> presented a paper on Viking Navigation. They mention the Greenland
> disk and note a rather poorly carved gnomon-like curve on it, but
> they really just raise the possibility that it is a sun compass.
>
> Both papers are published in "Vinland Revisited", ed. Shannon
> Lewis-Simpson, ISBN 0-919735-07-X. To connect the book to previous
> discussions on sa, it also has Alan Crozier's Vinland paper, and
> in its list of contributors confers the title Dr. to Birgitta Wallace.
--
p.a.
Eric Stevens
<v...@jamie-san.demon.co.uk> wrote:
>
>"Lech" <le...@nospam.pl> wrote in message news:e8g6vs$34g$1...@nntp.aioe.org...
>> U¿ytkownik "Vaughan Sanders" <v...@jamie-san.demon.co.uk> napisa³ w
>> wiadomo¶ci $8300...@news.demon.co.uk...
>snip
>>> >
>>>
>>> Going blind from looking directly at the sun was a major problem with
>> a
>>> cross-staff, particularly in northern latitudes with almost constant
>>> daylight, the back-staff solved this problem.
>>> http://www.mat.uc.pt/~helios/Mestre/Novemb00/H61iflan.htm
>>> The sun compass can be used to just determine latitude.
>>> Floating one in a pale of water would stabilize it in most sailing
>>> conditions, the noon discrepancy during the short sailing season is
>> +/- half
>>> a degree of latitude apparently.
>>> I used a pale of water to watch the last eclipse to protect my eyes.
>>>
>>> The half disc found in Greenland having a huge hole for the gnomon
>> would
>>> need explaining however
>>>
>> http://viking.sjolander.com:5150/wiki/index.php/Considerations_on_The_Viking_Sun_Compass..
>>>
>>> Is there a picture of the Polish sun compass on the net?
>>
>>
>> Yes it is:
>>
>> http://www.wolin.pl/informator/listopad/wiesci.html
>> http://www.zsee.bytom.pl/sciaga/przygotowanie.pdf
>>
>> Lech
>>
>> <<Nie chwal dnia przed zachodem slonca>>
>>
>
>Thanks.
>There doesn't appear to be a gnomon curve for it to be used as a compass,
The hyperbolic gnomon curve is the projection line of the shadow of
the tip of the gnomon at constant latitude. I have seen other
explanations of the use of the sun compass in which various seemingly
purposeless marks relate to the latitude of different parts of a
generally north-south running coast line. In other words the compass
can be used to help navigate to a latitude.
The site which gave this explanation seems to have gone but the marks
upon which it relied can be clearly seen in the illustrations of your
second URL below.
http://etimage.com/english/Medd14/solkompas/solkompas.htm
>this appears to make the Knox-Johnson comments meaningless.
>("In practice a perfectly satisfactory curve can be drawn from marks made at
>hourly intervals. You have now created a simple sun compass")
>http://members.aol.com/jvlambert/Norman/SunCompass.htm
>The two circles could however cover the deviation of latitude either side of
>summer solstice on lat 60 / 61 north.
>
>This site claims the Greenland dial is complete
>http://etimage.com/english/Medd14/solkompas/solkompas.htm
>
>Jamie.
>
>
Eric Stevens
Eric Stevens
I noted one interesting quotation from that site:
"One area that I have not shown Jim is the report by Bishop Olaus
Magnus, of Norway report to the Pope 1555. Quote: Here they are in
the habit of directing their voyage on varying routes over a long
sea voyage by the guidance of the gnomon; Endquote."
Elsewhere in this or a related thread there was a discussion about
whether or not a mystery object found on the Mary Rose may have been a
sun compass. PA (I think it was) suggested that the magnetic compass
was in use by that time and that the sun compass would therefore be
obsolete. The above quote shows that the sun compass still was in use
during the Mary Rose period.
Eric Stevens
Peter Alaca
Simon Pugh
<eric.s...@sum.co.nz> writes
My table was intended to show shadow length and the bearing of the sun
at different times of day. I used a 1cm pin length as that was what was
suggested on the website, although it does seem rather short.
Over a five hour period, the shadow length varied between 0.9 and 1.1 cm
and the bearing of the sun varied by 98 degrees.
If the tip of the shadow has to be placed on a line, and the length of
the shadow varies so little, it doesn't seem possible to get a bearing
with anything like the accuracy suggested in the article.
As I said before these figures were done for Iceland, the situation is
better further south as there is a greater variation in shadow length
with time.
This type of sun compass would be useless at the North Pole as the
altitude of the sun hardly varies during a day.
--
Simon Pugh
Remove X for mail
Eric Stevens
<egeha.is.a...@start.no> wrote:
>JerryT wrote:
>> "Peter Alaca" <P.A...@jul.nn> skrev i meddelandet
>> news:44abba9e$0$52595$dbd4...@news.wanadoo.nl...
>>> IE J wrote: news:C1Oqg.7793$E02....@newsb.telia.net
>>>
>>>> "Vaughan Sanders" wrote
>>>>> [...]
>>>>> The half disc found in Greenland having a huge hole for the gnomon
>>>>> would need explaining however
>>>>> [...]
>>>> Sorry Jamie it didn't take more than a half disc.
>>> Sure Inger. That's why the Greenland disk is more
>>> than a half and the Wolin disk is a full disc.
>>>
>>
>> Some old thoughts.
>> http://www.columbusnavigation.com/vdisk.shtml
>>
>
>Very nice, and so much in contrast to those who here who have so
>strong opinions that the Greenland half-circle is a sun compass.
>
>And to add to the uncertainty of the sun compass theory, at the
>Vinland Millenium Symposium (2000) two professors in Nordic
>Archaeology (Keller and Christensen) discussed an alternative
>possibility, that the disk was a "confession disk" (a help for
>priests in keeping count in the dark). As support for this theory
>they note that the disk was found in the ruins of a probable
>Benedictine convent, and that Vebæk (the finder) in a later
>publication (1991) notes the uncertainty with regard to the dating
>due to an unnoticed stratigraphy during the excavation so that the
>disk is far from certainly a 11th century object (it must be later
>to be a confession disk).
>
>Additionally the two note the far from accurate carving of the
>triangles on the disk, with a spacing varying from 4 to 9 mm with
>a probable total of 35 if the disk originally was a full circle
>(note than everybody excepting IEJ seems to agree that a medieval
>compass should have 32). Thus the disk is not made with the
>precision one should expect if it was intended to be used as a
>navigational instrument.
My own view always has been that the triangles round the edge could
never have been the 32 points of the compass. I've ignored those who
try to argue that they are. The fact that I (and others) don't know
their significance does not mean that they had none as far as the
original carver was concerned. I just don't know what it was.
>
>At the symposium Carl Roslund together with Thirslund and Páztor
>presented a paper on Viking Navigation. They mention the Greenland
>disk and note a rather poorly carved gnomon-like curve on it, but
>they really just raise the possibility that it is a sun compass.
>
>Both papers are published in "Vinland Revisited", ed. Shannon
>Lewis-Simpson, ISBN 0-919735-07-X. To connect the book to previous
>discussions on sa, it also has Alan Crozier's Vinland paper, and
>in its list of contributors confers the title Dr. to Birgitta Wallace.
>
Eric Stevens
Eric Stevens
wrote:
>Eric Stevens wrote: news:q6coa2hqv2utqj0sq...@4ax.com
Noted.
I relied on memory only because I didn't have time to go hunting.
Eric Stevens
Vaughan Sanders
I have no problem Inger, south is directly outside my front door, the shade
outside my backdoor is bit of a clue.
The problem arises in a sea mist or a white out on a mountain that you are
not familiar with, you quickly become disorientated
>>
>>
>> >If you happen to have a sun compass, which you and the
>> > other missed always has 180 degrees marked as 18 hacks for 10 degrees
> each
>> > on a half disc or half of the full disc, then you have an easy task to
>> > establish much easier than dividing the 90 degree angle in three which
> you
>> > can and people did in old days by making marks on the ship side.
>> >
>> > Inger E
>>
>> Seems a resonable way to divide 180, half the hack would give the 45
> (north
>> west for example), what did I miss?
>
> Yes you do. But then again you doesn't seem to understand the sun compass
> at
> all. Go back to 4th grades measuring with the half circle where 0 - 180
> degrees marked. You do exactly the same with the sun compass as you did
> when
> your teacher showed you how to measure angles. No problem.
>
> Inger E
>>
I'm not with you Inger, do you mean the sun-compass is just a protractor?
http://www.amblesideprimary.com/ambleweb/mentalmaths/protractor.html
Do you mean when I measure the pitch of a roof it also tells me where south
is?
Hmm, a plastic one might have reflected the sun into my eyes when I was
building my front gable, sun burn on my back would have been as good a clue
:-))
As I recall it was blowing a gale, pissing with rain and there wasn't a sign
of "currant bun".
I use Pythagoras every day Inger.
http://en.wikipedia.org/wiki/Pythagorean_theorem
3, 4, 5, is the simplest method to get a 90d angle, dividing the hypotenuse
of an isosceles triangle into 10 equal parts is not difficult.to make a
protractor with this calibration.
(The Greenland disc is not calibrated that accurately btw)
All compasses are just protractors that can establish a constant reference
point Inger, how do you sail 60 degrees (6 hacks) west of north if you can't
establish north?
The gnomon curve at lat 60'n is not correct at lat 50'n btw, and not correct
for the whole sailing season on a single latitude.
Jamie
Vaughan Sanders
Ever been in a whiteout on a mountain Inger?
http://en.wikipedia.org/wiki/Whiteout_(weather)
Jamie
Vaughan Sanders
"Simon Pugh" <Ne...@mrzsp.demonX.co.uk> wrote in message
news:LU7Kw7EA...@mrzsp.demonX.co.uk...snip
>>
>
> My table was intended to show shadow length and the bearing of the sun at
> different times of day. I used a 1cm pin length as that was what was
> suggested on the website, although it does seem rather short.
>
> Over a five hour period, the shadow length varied between 0.9 and 1.1 cm
> and the bearing of the sun varied by 98 degrees.
>
> If the tip of the shadow has to be placed on a line, and the length of the
> shadow varies so little, it doesn't seem possible to get a bearing with
> anything like the accuracy suggested in the article.
>
> As I said before these figures were done for Iceland, the situation is
> better further south as there is a greater variation in shadow length with
> time.
>
> This type of sun compass would be useless at the North Pole as the
> altitude of the sun hardly varies during a day.
>
> --
> Simon Pugh
> Remove X for mail
Presumably this is why many only see random scratches on the Greenland disc.
http://members.aol.com/jvlambert/Norman/SunCompass.htm
"The scaling of the Greenland sun compass indicates that the gnomon would
have been fairly short, about 0.52 cm ( 0.2 inches ) high"
Jamie
Simon Pugh
<v...@jamie-san.demon.co.uk> writes
The diagram on your site shows how little variation in shadow length
there is in the middle part of the day at 60deg N. It would have been
impossible to get an accurate bearing then.
But is the fragment really a sun compass? There seems to be a lot of
wishful thinking in the reconstruction. If the gnomon really would have
been 0.52cm the idea seems pretty ludicrous to me.
BernardZ
says...
> In article <fbOdndn_fNU...@pipex.net>,
> ken...@cix.compulink.co.uk says...
> > In article <MPG.1f1531aa7586e43a989a4d@news>, bern...@Nospam.com
> > (BernardZ) wrote:
> >
>
> (a)
>
> > > If I have a star, then I have a latitude. I don't need to know
> > > my position unless I go too far and miss the Island
> > > altogether.
> >
> > Losing track of longitude on ocean crossings could be fatal. Sir
> > Cloudsley Shovel <sp> managed to lose his life and a large part
> > of his fleet because of an error in longitude. Anson lost a large
> > part of his crew to scurvy because he got longitude wrong and
> > thus delayed land fall. Dampnier give accounts of where he ended
> > up on the wrong side of an island and was unable to beat back
> > against prevailing winds. He also makes the point that the
> > limiting factor on long voyages was scurvy.
> >
> > Ken Young
> >
>
> Mmmmmmmmmmmmmm
>
>
> Ken yet again you display a bad habit of jumping in without reading what
> people are saying. I have noticed it a lot.
>
> Okay you have missed the point but interestingly your answer confirms
> what I said.
>
> Lets get back to the topic. Firstly read what I wrote at (a). Digest it.
>
> Now say you leave Norway and go to Iceland.
>
> You look for the star, find it and set course for the star. So you go
> towards the correct latitude. Once there you stay at that latitude.
>
> Somewhere on the way, you get lost eg a storm drives you off course.
>
> As before you look for the star, find it and set course for the star. So
> you go towards the correct latitude. Again once there you stay at that
> latitude.
>
> We have two possibilities
>
> 1) You are between Norway and Iceland so it does not matter as you are
> going on the correct Latitude and will soon hit Iceland.
>
> 2) You have gone past Iceland, in which case like your Dampnier example
> above, you are in real trouble.
>
>
>
Oops
I should have added here Ken, that this problem only occurs when going
to an Island. If you go from Iceland to Norway. Its not an issue as
point (2) above cannot occur.
--
It is best to travel the path of life with some one else but its nice to
go alone for a short time.
Observations of Bernard - No 101
Erik Hammerstad
> Erik Hammerstad wrote: news:4h2mvcF...@individual.net
>
>> JerryT wrote:
>>> "Peter Alaca" <P.A...@jul.nn> skrev i meddelandet
>>> news:44abba9e$0$52595$dbd4...@news.wanadoo.nl...
>>>> IE J wrote: news:C1Oqg.7793$E02....@newsb.telia.net
>>>>
>>>>> "Vaughan Sanders" wrote
>>>>>> [...]
>>>>>> The half disc found in Greenland having a huge hole for the
>>>>>> gnomon would need explaining however
>>>>>> [...]
>>>>> Sorry Jamie it didn't take more than a half disc.
>>>> Sure Inger. That's why the Greenland disk is more
>>>> than a half and the Wolin disk is a full disc.
>>>>
>>>
>>> Some old thoughts.
>>> http://www.columbusnavigation.com/vdisk.shtml
>
>> Very nice, and so much in contrast to those who here who have so
>> strong opinions that the Greenland half-circle is a sun compass.
>>
>> And to add to the uncertainty of the sun compass theory, at the
>> Vinland Millenium Symposium (2000) two professors in Nordic
>> Archaeology (Keller and Christensen) discussed an alternative
>> possibility, that the disk was a "confession disk" (a help for
>> priests in keeping count in the dark). As support for this theory
>> they note that the disk was found in the ruins of a probable
>> publication (1991) notes the uncertainty with regard to the dating
>> due to an unnoticed stratigraphy during the excavation so that the
>> disk is far from certainly a 11th century object (it must be later
>> to be a confession disk).
>
> But as far as I have read Enterline's "White paper",
> the attribution to the site of the convent is not sure.
> And if it is from that site, it is probably from beneath
> the convent in disturbed ground.
>
No doubt regarding the find place is noted in the paper, but
uncertainty with regard to it being a convent is, as is the dating
of the disk. By the way, I'm fairly certain that the authors do
not really believe in their alternative theory, but that they
presented it just to show the uncertainty of the sun compass theory.
Peter Alaca
> Peter Alaca wrote:
>> Erik Hammerstad wrote:
>>>> "Peter Alaca" skrev
> No doubt regarding the find place is noted in the paper, ...
Yes there is, see e.g. Neil Good 28 Jan and 1 Feb 1998
e.g. in his 28 jan note
The article by C.L.Vebæk in the May 3, 1952,
"Illustrated London News" describes two
separate archaeological sites- "...a mediaeval
Benedictine nunnery beside the beautiful
Unartoq Fjord...", and four farms and two
churches in the "...Vatnahverfi District." The
photo-captions connected with the "Sun-Ray
Disk" and the "Gaming Pieces" suggests they
were all found in the Vatnahverfi area, NOT
under the nunnery. The text of the article also
implies everything found in Vatnahverfi was
found in the farmhouses.
> ... but
> uncertainty with regard to it being a convent is, as is the dating
> of the disk. By the way, I'm fairly certain that the authors do
> not really believe in their alternative theory, but that they
> presented it just to show the uncertainty of the sun compass theory.
That is not my impression.
In the first plase are Keith Pickering's calculations
a good arguments against it being a sun-dial, or at
least it's suitability as a sun-dial.
And on 9 Mar 98 he writes:
" If the argument is, "The artifact is a sun-
compass because it vaguely resembles a sun-
compass," then my response would be that it
vaguely resembles a lot of things.
For example, it resembles a bicycle sprocket,
too, but that doesn't prove that the Vikings had
bicycles.
If Thirslund intends to prove that the Vikings
had and used a sun-compass, then we should
expect to see evidence more convincing than a
Rorshacht test."
Neil Good, 1 Feb 1998
" For now I will say I am inclined more than ever
to identify it as a checker, plain and simple.
This does not mean however I am not open to
the suggestion it may have been a precision
navigational instrument at one time. I just
believe it started off as a checker, and ended
as a checker."
James Enteline on 5 Feb 1999:
" It is not necessarily implausible that the Norse
could have had a sun compass, but it probably
is implausible that this particular object was
one."
http://www.columbusnavigation.com/vdisk.shtml
--
p.a.
Erik Hammerstad
You misunderstood, my comments were with respect to the Keller and
Christensen paper.
Vaughan Sanders
"Peter Alaca" <P.A...@jul.nn> wrote in message
Hmmm, seems that Robin might be a bit biased.
"I asked around at the Viking Ship Museun yesterday about articles in
English on the sun compass problem and had a book stuck into my hands as an
answer. It is:
Søren Thirslund, _Viking Navigation_, Humlebaek 1997 (no indication in book
of year, I had to ask)
The author, who spent a good deal of his life as first mate on the royal
ship Dannebrog, has had help from two English naval officers (Sir Robin
Knox-Johnston and Lt. Commander W. Waters) and from Profesoor Sean McGrail.
He is a partisan of the sun compass theory. He loyally outlines the
arguments of Captain Soelver and dr. Roslund and does so in excellent
English. "
Anyone know the size of the Polish disc?
Jamie
Peter Alaca
> Hmmm, seems that Robin might be a bit biased.
What do you mean biased?
This is what he wrote:
" The first disc was discovered in Greenland in
1947, but in 2000 another was found in a
Viking site in Poland. Both date to about
1000AD and have gnomon curves scratched
on their surfaces."
http://www.robinknox-johnston.co.uk/da/20090
but I see no trace of a gnomon curve on the wolin disk.
http://www.wolin.pl/informator/listopad/wiesci.html
http://www.zsee.bytom.pl/sciaga/przygotowanie.pdf
> "I asked around at the Viking Ship Museun yesterday about articles in
> English on the sun compass problem and had a book stuck into my hands
> as an answer. It is:
>
> Søren Thirslund, _Viking Navigation_, Humlebaek 1997 (no indication
> in book of year, I had to ask)
>
> The author, who spent a good deal of his life as first mate on the
> royal ship Dannebrog, has had help from two English naval officers
> (Sir Robin Knox-Johnston and Lt. Commander W. Waters) and from
> Profesoor Sean McGrail. He is a partisan of the sun compass theory.
> He loyally outlines the arguments of Captain Soelver and dr. Roslund
> and does so in excellent English. "
>
> Anyone know the size of the Polish disc?
I think this means that is is 8cm:
" Drewniany dysk o s'rednicy 8 cm z
umieszczonym wewna;trz stoz.kiem pozwala?
na okres'lenie w?asnej pozycji na morzu oraz
wyznaczenie kierunku z.eglugi."
http://www.wolin.pl/informator/listopad/wiesci.html
--
p.a.
Lech
wiadomosci news:e8jrhb$a2t$1$8300...@news.demon.co.uk...
Did You not look at my link :
http://www.wolin.pl/informator/listopad/wiesci.html
Click on the photograph and You will see scale.
Peter Alaca
> "Vaughan Sanders" napisal w
>> Anyone know the size of the Polish disc?
> Did You not look at my link :
>
> http://www.wolin.pl/informator/listopad/wiesci.html
>
> Click on the photograph and You will see scale.
That means it is not 8 but c 8.5 cm
--
p.a.
Vaughan Sanders
"Lech" <le...@nospam.pl> wrote in message news:e8jvkr$rjs$2...@nntp.aioe.org...
Assuming the scale is centimetres then Peter's 8 cm seems correct, about the
same size as the Greenland disc.
Discs of this size, even calibrated with precision, are pretty useless as a
compass because of the small deviation in the gnomon curve.
People who could build ships with great precision would have made a better
job of calibrating the Greenland disc, even by eye I would have thought,
I wonder what size disc experimental historians use to get positive results?
Jamie
Lech
Yes, Peter understand very well Polish !
> Discs of this size, even calibrated with precision, are pretty useless
as a
> compass because of the small deviation in the gnomon curve.
If it is not a suncompass, what is it ?
> People who could build ships with great precision would have made a
better
> job of calibrating the Greenland disc, even by eye I would have
thought,
>
> I wonder what size disc experimental historians use to get positive
results?
>
> Jamie
Simon Pugh
<v...@jamie-san.demon.co.uk> writes
<snip>
>
>Assuming the scale is centimetres then Peter's 8 cm seems correct, about the
>same size as the Greenland disc.
>Discs of this size, even calibrated with precision, are pretty useless as a
>compass because of the small deviation in the gnomon curve.
>People who could build ships with great precision would have made a better
>job of calibrating the Greenland disc, even by eye I would have thought,
>
>I wonder what size disc experimental historians use to get positive results?
>
>Jamie
>
>
I just made myself a crude sun compass out of a semicircular piece of
cardboard with 10 cm radius and a 2 cm pin. It took about 10 mins using
a table of angles and lengths I made from Starry Night yesterday.
It is surprisingly easy to use with a horizontal surface to place it on.
I reckon I could get north/south to about +-10deg at 10 am, but this is
critically dependant on having a known horizontal surface to rest it on.
Probably similar accuracy to the small undamped pocket compass I
compared it with. Unfortunately experiments were curtailed by lack of
sunshine today.
It would be less accurate nearer noon as the rate of change in shadow
length is less.
Vaughan Sanders
"Lech" <le...@nospam.pl> wrote in message news:e8l7pi$ln9$1...@nntp.aioe.org...
snip
>>
>> Assuming the scale is centimetres then Peter's 8 cm seems correct,
> about the
>> same size as the Greenland disc.
>
> Yes, Peter understand very well Polish !
>
>> Discs of this size, even calibrated with precision, are pretty useless
> as a
>> compass because of the small deviation in the gnomon curve.
>
> If it is not a suncompass, what is it ?
snip
>
>
> Lech
>
> <<Nie chwal dnia przed zachodem slonca>>
>
They appear small enough to be gaming pieces, or candle holder is another
possibility.
The gnomon hole is way to large for a compass on both discs, I can't see why
you would bore the hole all the way through to fit a handle.
There appears to be some dispute over where the Greenland disc was found,
but the excavation was of a nunnery, candle holder would be just as likely
as a compass in a nunnery I would have thought.
Jamie