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: Hughes Tables
    From: Geoffrey Kolbe
    Date: 2007 Jun 07, 19:57 +0100
    Robert Eno wrote:

    Many thanks to d walden.
    As it turns out, part of the answer to my question was behind me on a bookcase full of navigation texts. Vol 3 of the Admiralty Manual of Navigation (1954) carries a brief description.
    On a quick glance and not being a mathematician, it appears that the sight reduction method in Hughes is similar to HO 211 (Ageton)?

    In Ageton's method, the perpendicular is dropped from the geographical position of the celestial body to made a right angle with the observer's meridian.

    The Hughes method drops the perpendicular from the observer's DR position to the meridian of the celestial body. In this, it is similar to the method used for the NAO tables used in the Nautical Almanac. Paul Janiczek, co-originator of the NAO tables (with Admiral Tom Davies), wrote a nice piece on how the NAO tables came into being in the last issue of the Navigator's Newsletter.

    The disadvantage of the Hughes' method (and others like it where the perpendicular is dropped from the observer's DR position to the meridian of the celestial body) is that the perpendicular splits the azimuth angle - the separate components of which have to be computed and added together, so increasing the number of steps involved. One advantage of the method (says Janiczek) is that the initial entry into the tables is with the Latitude and LHA, so all initial entries for all sightings will be on the same page, reducing the total number of page openings.

    It is worth noting that the formulae used in the NAO tables use just sines and cosines, and two sets of tables are required. Whereas, from the scanned page provided by D Walden, the Hughes tables seem to use sines and cosines; tangents and cotangents; secants and cosecants; which requires three sets of tables.

    Geoffrey Kolbe

    To post to this group, send email to NavList@fer3.com
    To unsubscribe, send email to NavList-unsubscribe@fer3.com

    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