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: Sunrise, Sunset, LAN, LMT
    From: Chuck Taylor
    Date: 2004 Aug 4, 21:17 -0700

    George Huxtable and Zorbec Legras pointed out that the
    method of finding longitude by equal altitudes before
    and after LAN is inexact.  I said as much, by
    describing it as falling into the category of
    "lifeboat navigation", by which I meant a method to be
    used when better methods are not available.  I also
    pointed out that it assumed minimal motion of the
    observer between observations.
    
    Despite the inexactness of the method, I find it
    interesting as an exercise in understanding the basic
    concepts involved.
    
    Best regards,
    
    Chuck Taylor
    North of Seattle
    
    
    --- George Huxtable  wrote:
    ...
    >
    > Chuck Taylor wrote-
    >
    > >In theory, if you had an accurate timepiece and
    > could
    > >observe the exact instant that the sun crosses your
    > >meridian (when it reaches its highest point), you
    > >could  then calculate your longitude by converting
    > >time to arc.
    >
    > The exact instant at which the Sun crosses your
    > meridian is NOT the same as
    > the moment that it reaches its highest point.
    > There's a correction to be
    > made, to account for any North-South component of
    > the observer's speed, and
    > also to allow for changing declination of the Sun.
    > For the non-critical
    > timing of the moment to measure altitude (for
    > latitude), that correction is
    > unnecessary, but for any determination of longitude
    > it has to be included.
    >
    > =================
    >
    > Zorbec Legras wrote-
    >
    > >Attention de greatest sun altitude is Not the
    > instant of transit for a
    > >mobile observer.
    >
    > Nor is the instant of greatest Sun altitude (quite)
    > the same as the instant
    > of meridian transit, even for a stationary observer
    > (except at the
    > solstices), due to the changing declination of the
    > Sun. But it's close.
    >
    
    
    __________________________________________________
    Do You Yahoo!?
    Tired of spam?  Yahoo! Mail has the best spam protection around
    http://mail.yahoo.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