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: Jack Aubrey's fixing of longitude
    From: Geoffrey Kolbe
    Date: 2011 Jun 21, 06:14 +0100

    At 23:54 20/06/2011, Albert wrote:
    >Well, I still remember the explanation Jack gave me about the
    >procedure for the intended observation...
    >The idea was to determine the exact local time for the moon set.
    >Previously - and using the data contained in the Nautical Almanac -
    >he had calculated the local time of this event for the estimated
    >island position.
    >The difference between the estimated and the actual moon-set local
    >time was then used to lay down the island. The exact local time of
    >this observation was determined with the aid of the chronometers
    >(good enough for the short time period since noon).
    >"Two seven four" was the azimuth of the moon when her lower lobe
    >touched the horizon. This fits very well with the described
    >situation (Venus above the moon).
    Using moon-set to find time is a laudable idea - but if I were doing
    it, I would find the highest hill and perch myself on top of that.
    Even doing the observation from the ship's tops would have been
    better than the shore. Finding the height of the hill above sea level
    would be needed of course, but that would not have been difficult.
    And why would the azimuth have been so important for a timing
    observation? I am afraid I don't see that.
    Geoffrey Kolbe

    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