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
    Name or NavList Code:
    Email:
       
    Reply
    Re: Impressed with the Raft Book
    From: Christian Scheele
    Date: 2010 Jan 28, 12:42 +0200

    I remember talking to Brad Morris and Frank Reed about this topic a few months 
    ago on this forum. They gave me some good insights into how refraction 
    affects observed altitudes. I hope to get to a value for latitude within a 
    narrow error margin should I proceed with my attempts to measure a day's 
    length.
    
    Christian Scheele
    Cape Town
    
     ----- Original Message -----
    From: "Brad Morris" 
    To: NavList@fer3.com
    Sent: Wednesday, January 27, 2010 6:51:22 PM GMT +02:00 Harare / Pretoria
    Subject: [NavList] Re: Impressed with the Raft Book
    
    Gentlemen
    
    This topic has been discussed extensively by many parties on the list, for a 
    substantial period.  The consensus of opinion is that you can generally 
    achieve about 1 degree of latitude.  Frank Reed points out that there is a 
    fish tracker that uses exactly this feature (latitude by length of day).
    
    The inaccuracies principally revolve around low altitude refraction of the sun 
    (just when is that sunrise, and precisely when was that sunset) and the 
    declination of the sun (this function breaks down as the declination of the 
    sun approaches zero).  So for the case indicated below, we are far from zero 
    declination.  Further, how was sunrise and sunset determined?  Harare, South 
    Africa is quite far from either the Atlantic Ocean for sunset or from the 
    straits between Africa and Madagascar for sunrise.    I share Christian's 
    description of this as a 'feat' and would look to further information to 
    clarify.
    
    Best Regards
    Brad
    
    
    
    
    "Confidentiality and Privilege Notice
    The information transmitted by this electronic mail (and any attachments) is 
    being sent by or on behalf of Tactronics; it is intended for the exclusive 
    use of the addressee named above and may constitute information that is 
    privileged or confidential or otherwise legally exempt from disclosure. If 
    you are not the addressee or an employee or agent responsible for delivering 
    this message to same, you are not authorized to retain, read, copy or 
    disseminate this electronic mail (or any attachments) or any part thereof. If 
    you have received this electronic mail (and any attachments) in error, please 
    call us immediately and send written confirmation that same has been deleted 
    from your system. Thank you."
    
    
    
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Get a NavList ID Code

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.

    Retrieve a NavList ID Code

    Enter the email address associated with your NavList messages. Your NavList code will be emailed to you immediately.
    Email:

    Email Settings

    NavList ID 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