Welcome to the NavList Message Boards.


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

Compose Your Message

Add Images & Files
    Re: No Lunars Era
    From: Alexandre Eremenko
    Date: 2004 Dec 6, 13:27 -0500

    On Mon, 6 Dec 2004, Ken Muldrew wrote:
    > On 5 Dec 2004 at 16:29, Alexandre Eremenko wrote:
    > Professional astronomers and surveyors had no difficulties with reducing
    > their own sights. The problems with the L&C data were not due to any
    > inherent problem with lunars per se.
    As I understand the story, L&C were specially taught by
    the best available teachers how to do lunars.
    Still they:
    a) did not understand that it is desirable to take altitudes
    (even for the simple reason that taking altitudes reduces
    the amount of calculations). I do not accept the argument that
    "they had other more important things to do". Look how many
    sights they took!
    b) tried and were unable to reduce their own sights.
    Then, they brought the results of their observations to the
    same highly qualified teachers to reduce... and we know
    what was the result.
    From my point of view this story demontrates that the method was
    too complicated for an average XIX century mariner.
    > I've done quite a few lunars using only an almanac, log tables, and pencil
    > & paper (using old methods such as Witchell's and Maskelyne's for clearing
    > the distance). It usually takes me 45-60 minutes from start to finish
    > (including the lunar sights, but not a time sight).
    This does not disprove my opinion stated above:-)
    My undergraduates can solve some problems that puzzled Euler
    or Archimedes:-)
    > tables were in common use and arithmetic calculation was heavily drilled
    > at school,
    Norie's 1828 book begins with a special chapter on "decimal
    I doubt this would be necessary if "arithmetic calculation was heavily
    drilled at school at that time":-)
    > Confidence in the result would come from comparing the lunar
    > longitude with the ded reckoning.
    I suppose you could check your lunars against GPS or some other
    modern tool. I am very curious to know what was the average error?
    (I mean, the error in the measurement of the distance).
    P.S. 1828 Norie is especially interesting to me, not only because of
    navigation, but also from the point of view of my main profession:
    mathematical education. It tells me a lot about the general state
    of mathematical education in England in the beginning of XIX century...
    The XX century books in navigation do not explain decimal arithmetic,
    and they use formulas instead of "word recipes". Just try to forget
    all you know, and follow one of the Norie recipes for reducing lunars:-)

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    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 Settings

    Posting Code:

    Custom Index

    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