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
    "Time Sights" and Lines of Position
    From: Doug MacPherson
    Date: 2016 May 15, 11:54 -0700

    I learned the "logarhythm" method of computing a "time sight" from a 1938 copy of Bowditch.  The chapter on "time sights" shows you how to compute your Longitude based on a DR Latitude, but does not show you how to obtain a Line of Position.  

    As has been pointed out by Frank and others in previous posts, a LOP can be easily obtained from the "time sight" information at hand by computing the Azimuth.  I like to use the ABC tables in my 1991 copy of Norie's which requires LHA, Latitude and Declination as inputs.  You can certainly use logarhythms as well for the computation using the equation [SinZ=sin(t) cos(d) sec (h)].

    My question concerns the 19th century practices.  Did those navigators commonly obtain an LOP after the "time sight" calculation by computing an azimuth?  Or was this pretty unheard of?  if not a pracitice, was this because they prefered  to keep their charts free from LOP lines, or had they never been introduced to the LOP possibility?  Other reasons?

    Cheers

    Doug

       
    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