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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.





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.


This file is part of a collection of files called Stefan's Florilegium. These files are available on the Internet at: http://www.florilegium.org


I have done  a limited amount  of  editing. Messages having to do  with separate topics  were sometimes split into different files and sometimes extraneous information was removed. For instance, the  message IDs  were removed to save space and remove clutter.


The comments made in these messages are not necessarily my viewpoints. I make  no claims  as  to the accuracy  of  the information  given  by the individual authors.


Please respect the time  and  efforts of  those who have written  these messages. The copyright status  of these messages  is  unclear  at this time. If information  is  published  from  these  messages, please give credit to the originator(s).


Thank you,

   Mark S. Harris                  AKA:  THLord Stefan li Rous

                                         Stefan at florilegium.org



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





       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



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.



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


International Marine, an imprint of TAB books. TAB Books is a division of

   McGraw-Hill (800)233-1128

ISBN 0-07-021120-5




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








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



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



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





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:



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




<the end>

Formatting copyright © Mark S. Harris (THLord Stefan li Rous).
All other copyrights are property of the original article and message authors.

Comments to the Editor: stefan at florilegium.org