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: Margetts' 1790 Longitude Tables
    From: Frank Reed
    Date: 2018 Jan 26, 10:55 -0800

    Ed, here's a pdf copy:

    Seemingly a great idea, these graphical tables had few fans. I speculate that there are several reasons for this:

    • Prohibitive expense. Cutting plates to print graphics like this was very expensive in that period, and since there was no other financial support, the tables had to pay their own way, so George Margetts put them on the market at a high price.
    • Relative ease of standard paper methods developed around this time. Using the streamlined version of Lyons' method which evolved into the methods of Mendoza Rios and Bowditch in one direction and the methods of Turner and Thompson (also copied by Bowditch) in another direction, it really wasn't much work to clear lunars without these exotic, expensive graphics.
    • Mediocre accuracy. There's some inherent reading inaccuracy when looking up values in these graphical tables, and also there may be some reduced quality in the calculations that produced them (I haven't looked into this in enough detail to say so firmly).

    Frank Reed
    Clockwork Mapping / ReedNavigation.com
    Conanicut Island USA

       
    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