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: Transcription of Worsley's Log
    From: Paul Hirose
    Date: 2009 Mar 05, 15:08 -0800

    George Huxtable wrote:
    > That's an odd way to denote a Greenwich time after Greenwich noon, isn't it?
    > Remember, in those days, the Greenwich day started at Greenwich mean noon,
    > so 0 hrs GMT for 24th April corresponded to noon, halfway through the civil
    > day of  24th April. That was the way Greenwich dates and times were noted in
    > almanacs of that era, recorded in Astronomical Time, which ran 12 hours
    > later than ordinary civil time.
    
    You're correct that zero hours astronomical time came 12 hours after
    zero hours civil time of the same date. But that made the astronomical
    time of an event 12 hours *earlier* (i.e., less than) than the
    corresponding civil time.
    
    One way to remember the difference between the astronomical, civil, and
    nautical day is to arrange the names in alphabetical order: 0000
    astronomical = 1200 civil = 2400 nautical (same date for all).
    
    The change to the meaning of GMT commencing in 1925 was controversial.
    For example, in 1921 The Observatory published several letters to the
    editor on the subject:
    
    http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?ref_stems=Obs....44&jou_pick=YES&return_req=no_params&end_year=2009
    (Search the page for the word "time", and note that the articles are in
    reverse chronolgical order.)
    
    --
    I filter out messages with attachments or HTML.
    
    --~--~---------~--~----~------------~-------~--~----~
    Navigation List archive: www.fer3.com/arc
    To post, email NavList@fer3.com
    To unsubscribe, email NavList-unsubscribe@fer3.com
    -~----------~----~----~----~------~----~------~--~---
    
    

       
    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