nav-inst-msg - 1/8/17

Period navigational instruments and navigation.

NOTE: See also the files: med-ships-art, ships-bib, Seakeeping-p1-art,  ships-msg, boat-building-msg, Nav-Crosstaff-art, travel-foods-msg.

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This file is a collection of various messages having a common theme that I  have collected from my reading of the various computer networks. Some messages date back to 1989, some may be as recent as yesterday.

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    Mark S. Harris                  AKA:  THLord Stefan li Rous
                                          Stefan at florilegium.org
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From: whheydt at PacBell.COM (Wilson Heydt)
Date: 21 Oct 91 22:49:58 GMT
Organization: Pacific * Bell, San Ramon, CA

moonman at buhub.bradley.edu (Craig Levin) writes:
>I am interested in the study of medieval navigation techniques.
>However, the books I have found about astronomy of the time deal
>mainly with cosmological theory and not the scientific practices of
>the time. Does anyone else here have an interest in this as well?

One place to start would be the History of Navigation section of _The
American Practical Navigator_ by Nathaniel Bowditch.  The edition I
have is the 1967, but the work has been kept in print by the US Navy
since 1867 (the book--in it's original form--actually goes back to
1803).

        --Hal

        Hal Ravn, Province of the Mists, West Kingdom
        Wilson H. Heydt, Jr.,  Albany, CA 94706,  415/524-8321 (home)


From: jartificer at aol.com (Jartificer)
Newsgroups: rec.org.sca
Subject: Re: Instruction for using a SexTent
Date: 19 Jan 1996 06:24:39 -0500

If you are talking about Sextants (as in navigation), there are plenty of
books on sailing, navigation, and such.
If you are interested for SCA purposes, keep in mind that sextants are a
little too late, even by the 1650 limit.  The immediate ancestor of the
sextant is the Backstaff, which looks somewhat similar but is much larger
and works in a slightly different way.  I just saw a bunch of them in the
UK while reseraching astrolabes, quadrants, sundials and such. They were
all made by instrument makers, who upgraded their wares with new
technology, much as we are switching to GPS.

Have fun
John the Artificer
John Rose


From: chk at primenet.com (Chris Kurtz)
Newsgroups: rec.org.sca
Subject: Re: Instruction for using a SexTent
Date: 19 Jan 1996 16:11:02 -0700

darknite at usa.net (Michael Martin) wrote:
>I am looking for onstruction in the proper use of a Sextent.  I any one 
>has a copy and wont mind uploading them to me I would greatly appreciate 
>it.

You might also try http://www.drake.edu/public/awb001/sail.html on the
World Wide Web.

+------------------------------------------------------------------------------+
| Chris H. Kurtz (blue at rocinante.com)            http://www.primenet.com/~blue |
|   Known in the Society as Lord Kristoff McLain Cameron                       |
|     Member of Duchy Aquitaine, Khanate Jaded Axe and First Mate of the I.B.B.|
+------------------------------------------------------------------------------+


From: david.razler at compudata.com (DAVID RAZLER)
Newsgroups: rec.org.sca
Subject: Re: period sextant? Answer
Date: Mon, 22 Jan 96 18:35:00 -0400
Organization: Compu-Data BBS -=- Turnersville, NJ -=- 609-232-1245

CK>>I am looking for onstruction in the proper use of a Sextent.  I any
CK>one  >has a copy and wont mind uploading them to me I would greatly
CK>appreciate  >it.

For *period* navigational gear, get ahold of "Chaucer [yes,the Goeffrey 
Chaucer] on the Astrolabe with Original Illustrations" available in 
Middle English or a 1931 Modern English edition published by Oxford 
University Press or the revised edition (1977) self-published by Norman 
Greene (Box 7657/ Berkeley, Ca. 94707 or (415) 524-1109)) He may (if in 
a good mood) offer to sell you some of his reconstructions which, though 
accurate, are expensive.

If you happen to find an original Middle English first edition printed 
by Caxton, I'll be only too glad to trade it for a modern translation 
<sick grin>

Seriously, the ME may be available on the Web either through The Chaucer 
Project or Project Gutenberg as the copyright has long expired.

Also I *think* the Gies's Cathedral, Forge and Waterwheel makes mention 
of early navigational instruments, as do several episodes of James 
Glenk's Connections broadcast every month or so on The Learning Channel. 
Both of the above are purely secondary sources, but hey...

                        In Service
                  Aleksandr the Traveller
                 [david.razler at compudata.com]


From: "David K. Schreur" <baronfum at net-link.net>
Newsgroups: rec.org.sca
Subject: Re: period sextant? Answer
Date: 24 Jan 1996 00:08:29 GMT

Of course, the sextant was not used intil very late if at all in period. Aleksandr has given the best advice in looking up Chaucer on the astrolabe, which was the chief method of determining latitude in later period.  Another instrument of navigation which is quite easy to recreate is the "Jacob's ladder" which consisted of a marked stick with a sliding crosspiece which was used for making sightings.  And, of course, longitude simply could not be determined in period and was not accurately determined until the refinement of an accurate chronometer.


From: clevin at ripco.com (Craig Levin)
Newsgroups: rec.org.sca
Subject: Re: Navigation - maps and instruments
Date: 6 Feb 1997 05:16:54 GMT
Organization: Ripco Internet BBS, Chicago

Matthew Legge  <mlegge at quokka.epidem.uwa.edu.au> wrote:

>I was wondering if any one could help me with some research I am doing. 
>The subject is maritime navigation, the methods and instruments used. I 
>have found one good source, but it focuses on ships and their design. Is 
>there any one out on the ether who can direct me to any SCA publications 
>on the subject or any person who has looked into this subject.

Given that the SCA's period stretches from the end of the Roman
_classes_ to the Great Armada, the question of navigation isn't
an easy one to answer. My own research has mostly concentrated on
the Age of Exploration, and even more specifically on the voyages
and voyagers of the Iberian Peninsula, more on Portugal than on
Aragon or Castile.

A fair introductory work to the entire sweep of mediaeval
seafaring was written by the late Archibald Lewis. IMO, his
European Naval and Maritime History belongs in every college
library, and mine, too, if I can find a way to get it cheaply. 

If you wish to look into my half-acre of maritime history, you're
more than welcome! Start with Hale's Renaissance Exploration, and
Parry's Age of Reconnaisance, and Brown's Story of Maps. Samuel
Eliot Morison's Admiral of the Ocean Sea, while focussing on
Cristobal Colon, is also a worthy work to keep near at hand, for
Morison was a yachtsman, and sailed many of the same seas that
Colon did.
--
http://pages.ripco.com:8080/~clevin/index.html 
clevin at ripco.com
Craig Levin


Newsgroups: rec.org.sca
From: brandt at dca.net (Keith E. Brandt)
Subject: Re: Navigation - maps and instruments
Date: Mon, 10 Feb 97 17:38:51 GMT

There is a fairly recent book called "Latitude Hooks and Azmuth Rings" which 
discussed how to build working replicas of early navigation instruments. There 
are a few primitive tools, but most are 1500 and later. I don't have the 
author or ISBN of the book handy, but can supply it if necessary.

Galen of Ockham
Friar, Chirurgeon, Pilot, and sometimes Fighter
Shire of Caer Adamant
East Kingdom


Newsgroups: rec.org.sca
From: brandt at dca.net (Keith E. Brandt)
Subject: Re: Navigation - maps and instruments
Date: Thu, 13 Feb 97 02:55:11 GMT

I received a few queries by email, so here's the full reference

Latitude Hooks and Azimuth Rings
   How to build and use 18 traditional navigational tools
Dennnis Fisher
1995
International Marine, an imprint of TAB books. TAB Books is a division of 
     McGraw-Hill (800)233-1128
ISBN 0-07-021120-5

--Galen
--------------------------------------------------------------------
Galen of Ockham
Friar, Chirurgeon, Pilot, and sometimes Fighter
Shire of Caer Adamant
East Kingdom
===============================================================================
Keith E. Brandt, MD, WD9GET      ||  I don't really care if they label me a
 Major, Flight Surgeon           ||     Jesus Freak,
Dover AFB, Delaware              || 'Cause there ain't no disguisin' the truth! 
brandt at dca.net                   ||  
http://www.dca.net/~brandt       ||                                --DC Talk
===============================================================================


From: Jeremy Johnson <phlagm at gmail.com>
Date: January 31, 2011 8:11:16 AM CST
To: Barony of Bryn Gwlad <bryn-gwlad at lists.ansteorra.org>
Subject: [Bryn-gwlad] In Nature today - Did Vikings navigate by polarized light?

Hey all.  I know I've been absent for a while, but I saw this first
thing this morning and thought I would pass it along.  But since I
don't know how many of you have access to nature articles, I decided
to just go ahead and  copy, paste, and post the whole thing to the
list:  Having spent some winters in Germany lately, I can attest to
having experienced periods of several days where the entire sky is
dull grey and gives absolutely no indication of the direction of the
sun.

Enjoy

-Sigthorn

--------------------------------------------------------------------------------
Did Vikings navigate by polarized light?

'Sunstone' crystals may have helped seafarers to find the Sun on cloudy days.

Jo Marchant

A Viking legend tells of a glowing 'sunstone' that, when held up to
the sky, revealed the position of the Sun even on a cloudy day. It
sounds like magic, but scientists measuring the properties of light in
the sky say that polarizing crystals — which function in the same way
as the mythical sunstone — could have helped ancient sailors to cross
the northern Atlantic. A review of their evidence is published today
in Philosophical Transactions of the Royal Society B1.

The Vikings, seafarers from Scandinavia who travelled widely and
settled in swathes of Northern Europe, the British Isles and the
northern Atlantic from around 750 to 1050 AD, were skilled navigators,
able to cross thousands of kilometres of open sea between Norway,
Iceland and Greenland. Perpetual daylight during the summer sailing
season in the far north would have prevented them from using the stars
as a guide to their positions, and the magnetic compass had yet to be
introduced in Europe — in any case, it would have been of limited use
so close to the North Pole.

But Viking legends, including an Icelandic saga centring on the hero
Sigurd, hint that these sailors had another navigational aid at their
disposal: a sólarsteinn, or sunstone.

The saga describes how, during cloudy, snowy weather, King Olaf
consulted Sigurd on the location of the Sun. To check Sigurd's answer,
Olaf "grabbed a sunstone, looked at the sky and saw from where the
light came, from which he guessed the position of the invisible Sun"2.
In 1967, Thorkild Ramskou, a Danish archaeologist, suggested that this
stone could have been a polarizing crystal such as Icelandic spar, a
transparent form of calcite, which is common in Scandinavia2.

Light consists of electromagnetic waves that oscillate perpendicular
to the direction of the light's travel. When the oscillations all
point in the same direction, the light is polarized. A polarizing
crystal such as calcite allows only light polarized in certain
directions to pass through it, and can appear bright or dark depending
on how it is oriented with respect to the light.

Centred on the light

Scattering by air molecules in the atmosphere causes sunlight to
become polarized, with the line of polarization tangential to circles
centred on the Sun. So Ramskou argued that by holding a crystal such
as calcite up to the sky and rotating it to check the direction of
polarization of the light passing through it, the Vikings could have
deduced the position of the Sun, even when it was hidden behind clouds
or fog, or was just beneath the horizon.

Historians have debated the possibility ever since, with some arguing
that the technique would have been pointless, because it would only
work if the crystal was pointed at patches of clear sky, and in such
conditions it would be possible to estimate the position of the Sun
with the naked eye, for example from the bright lining of cloud tops3.

Gábor Horváth, an optics researcher at Eötvös University in Budapest,
and Susanne Åkesson, a migration ecologist from Lund University,
Sweden, have been testing these assumptions since 2005. The special
issue of Philosophical Transactions of the Royal Society B in which
their review appears is dedicated to biological research on polarized
light1.

In one study, the researchers took photographs of partly cloudy or
twilight skies in northern Finland through a 180° fisheye lens, and
asked test subjects to estimate the position of the Sun4. Errors of up
to 99° led the researchers to conclude that the Vikings could not have
relied on naked-eye guesses of the Sun's position.

To check whether sunstones would work better, in 2005 they measured
the polarization pattern of the entire sky under a range of weather
conditions during a crossing of the Arctic Ocean on the Swedish
icebreaker Oden5,6.

Through the clouds

The researchers were surprised to find that in foggy or totally
overcast conditions the pattern of light polarization was similar to
that of clear skies. The polarization was not as strong, but Åkesson
believes that it could still have provided Viking navigators with
useful information.

"I tried such a crystal on a rainy overcast day in Sweden," she says.
"The light pattern varied depending on the orientation of the stone."

She and Horváth are now planning further experiments to determine
whether volunteers can accurately work out the Sun's position using
crystals in various weather conditions.

Sean McGrail, who studied ancient seafaring at the University of
Oxford, UK, before retiring, says that the studies are interesting but
there is no real evidence to indicate that the Vikings actually used
such crystals. "You can show how they could be used, but that isn't
proof," he says. "People were navigating long before this without any
instruments."

Surviving written records indicate that Viking and early medieval
sailors crossed the north Atlantic using the Sun's position on clear
days as a guide, in combination with the positions of coastlines,
flight patterns of birds, migration paths of whales and distant clouds
over islands, says Christian Keller, a specialist in North Atlantic
archaeology at the University of Oslo. "You don't need to be a
wizard," he says. "But you do need to combine a lot of different sorts
of observations."

Keller says he is "totally open" to the idea that the Vikings also
used sunstones, but is waiting for archaeological evidence. "If we
find a shipwreck with a crystal on board, then I would be happy," he
says.

References

Horváth, G. et al. Phil. Trans. R. Soc. B 366, 772-782 (2011).
Ramskou, T. Skalk 2, 16-17 (1967).
Roslund, C. & Beckman, C. Appl. Opt. 33, 4754-4755 (1994).
Barta, A. , Horváth, G. & Meyer-Rochow, V. B. J. Opt. Soc. Am. A22,
1023-1034 (2005).
Hegedüs, R. , Åkesson, S. , Wehner, R. & Horváth, G. Proc. R. Soc.
A463, 1081-1095 (2007).
Hegedüs, R. , Åkesson, S. & Horváth, G. J. Opt. Soc. Am. A 24,2347-2356 (2007).


Date: Tue, 1 Feb 2011 18:37:53 -0500
From: Bill Ford Hotmail <wcford at hotmail.com>
To: <atlantia at seahorse.atlantia.sca.org>
Subject: Re: [MR] Did Vikings Navigate by Polarized Light?

Here is the reference to the full article:
http://rstb.royalsocietypublishing.org/content/366/1565/772 

The upshot of the article is that while the theory is plausible, more
research is necessary, especially in order to determine the errors
associated with the positions measured using such methods. As a physicist, I
would caution that using natural crystals, which the Vikings certainly
would, the accuracy would suffer MUCH more than is likely to be calculated
or measured using modern methods. Natural crystals have defects which are
not in crystals that are grown in manufacturing facilities today.
Nevertheless, it is an intriguing idea and I will be interested to see how
their research proceeds.

--Dr. William C. Ford
(William Scolari - Barony of Bright Hills)


From: erhoover at WAMEGO.NET
Subject: Re: [CALONTIR] In seach of a Maritime Guild
Date: June 25, 2011 1:19:33 PM CDT
To: CALONTIR at listserv.unl.edu

Miklos; Have you looked at the book - "Attitude Hooks and Azimeth Rings ; 
How to build and use 18 traditional navigational tools." by Dennis Fisher

I have it and am looking at several projects to build , although for me in the 
14th c., very few navigational instruments were avaliable/used.

Another good book is: "The World of the Medieval Shipmaster ; Law, 
Buisness and the Sea, c.1350-1450" by Robin Ward

E'douard

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Edited by Mark S. Harris	nav-inst-msg	Page 8 of 8