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: Beginner Meridian Passage Question
    From: Michael Dorl
    Date: 2004 Sep 9, 08:39 -0500

    Somebody gave me a book called 'Latitude Hooks and Azimuth Rings' by Dennis Fischer publisher International
    Marine.  In it he describes several old instruments and gives directions for making them.  Included is a device
    called a Nocturnal.  The Nocturnal came in many forms, the one Fischer describes is useful for...

      determining local time by observing the position of Ursa Major (or Minor) with respect to Polaris

      determining the correction to be applied to the height of Polaris to determine latitude again by
      observing the position of Ursa Major (or Minor) with respect to Polaris.

      calculating the position of the moon given the local time, date, and day of lunar month.  Useful for predicting
      local high and low tides times.  EG. When should I leave port on a given date to sail on the falling
      tide.

    I made one and its actually quite good at determining local time, it's easy to come within 10 minutes.  The
    Polaris correction is more than good enough to get you within 5 minutes of angle.

    see http://brunelleschi.imss.fi.it/genscheda.asp?appl=SIM&xsl=multimed&lingua=ENG&chiave=500044

    If you want the book see http://www.celestaire.com/catalog/products/5722.html or many other sources.
    Search for Latitude Hooks and Azimuth Rings Dennis Fischer for other sources.

    I'd think a Nocturnal or a sketch of the position of Ursa Major and Ursa Minor at Polaris meridian crossing would
    be a useful life boat adjunct.
       
    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