Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: No sextant, no watch, no almanach, nothing
    From: Trevor Kenchington
    Date: 2004 Nov 5, 23:56 -0400

    Alex,
    
    Geoffrey's method would need a star catalogue but not necessarily an
    almanac. Since the stars are fixed (at the level of precision of
    instrument-free navigation), the declinations of the brighter ones can
    be learnt with relatively little difficulty. (Equivalent knowledge,
    though not expressed as "declinations", formed a key component of
    traditional Polynesian navigation. It didn't need the support of
    astronomers, telescopes and printed tables of numbers.)
    
    Determination of the zenith without a sextant is said to be possible by
    lying on deck, sighting up the mast, and visually averaging the position
    of the masthead against the sky. However, I think I would rather
    memorize the stars with declinations equal to my chosen co-latitude.
    When on the intended parallel, those stars should of course be just
    circumpolar, grazing the horizon at each inferior meridian passage --
    something that could be observed with reasonable precision at tropical
    and temperate latitudes.
    
    Or you can make a kemal suited to the latitude you are planning to sail
    down, particularly if it is in the northern hemisphere and Polaris is
    available.
    
    
    Trevor Kenchington
    
    
    You wrote:
    
    > Dear Geoffrey,
    > I am not sure that I really understand the details of the method you
    > describe but it seems to be based on the almanac.
    > The people you mention just used the almanac BEFORE
    > their trip to select the stars.
    >
    > In principle, you can memorize some data from the almanac,
    > then leave the almanac at home and use the data from your
    > memory:-)
    >
    > For example, the hero of Mark Twain novel "Yankee at the court of
    > king Arthur" memorized the day and time of a solar eclipse:-)
    >
    > (He just happened to read an almanac before his travel.)
    > I would not call this "navigation without almanac".
    >
    > Second, how do you detect without a sextant when a star it in zenith?
    > I don't think this is easy to do.
    >
    > Alex.
    
    
    --
    Trevor J. Kenchington PhD                         Gadus{at}iStar.ca
    Gadus Associates,                                 Office(902) 889-9250
    R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
    Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555
    
                         Science Serving the Fisheries
                          http://home.istar.ca/~gadus
    
    
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site