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: lat/long from meridian passage
    From: Jeremy C
    Date: 2011 Jan 25, 21:49 EST
    The idea is pretty basic.  You determine Longitude based on your measured time of LAN.  The trouble is that the when you or the sun are moving N/S while shooting all of the sights, the curve of the apparent altitude is displaced a bit giving you the wrong time of LAN, there therefore longitude.
    The method of Lat and Long at transit works best when you are stationary and the sun is near the solstice (changing declination very little).  The method works fairly well with the planets since their change of declination is usually small.  It would work well with stars if you actually observe them over a long twilight.  The moon is probably an exercise in futility without a computer as the declination changes fairly dramatically. 
    You can still use the method but corrections for the various bodies' change in declination and your motion are needed.
    In a message dated 1/24/2011 10:07:24 P.M. Central Asia Standard Tim, goold@vwc.edu writes:
    That is not surprising, since I don't understand the effect of declination change on determination of longitude.  At this point, I am abstracting from as much change as I can.  I am trying to wrap my little brain around the problem of determining the longitude of my front garden.  The problem of establishing the longitude of a vessel in motion is too much at this point.   I would be happy to be instructed, however.  That is the change you are talking about, isn't it-- the observer in motion?


    On Mon, Jan 24, 2011 at 12:23 AM, James N Wilson <jn.wilson@juno.com> wrote:

    You still haven't shown that you understand the effect of declination
    change on the determination of longitude. But you're with the majority.

    Jim Wilson
    Go Wesleyan College
    Norfolk, VA 23502
    757 455 3357

    Charles Olson: "Love the World -- and stay inside it."

    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)