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: Can I Navigate Without an Assumed Position?
    From: John D. Howard
    Date: 2017 Aug 25, 08:08 -0700

     Calvin,

    I re-read your message and decided to answer your question - Can one determine their Lat / Lon with only a sextant.  The answer is No.

    The sextant is only one tool used for position finding.  What is needed in addition is an almanac of some kind and a way to tell time.  Without a way to tell the time you cannot figure longutide because for all practical purposes longitude is time.

    The almanac can be as simple as a one page table of declination of the sun and the equation of time.  The way to tell time can be a watch, clock, radio, or any known event  - like an eclipse.

    I assume you want to learn cel-nav as a modern navigator would, and not as a shipwrecked person on Gillian's Island.  Most people know about where there are in general terms, and that is good enought for an Assumed Position.  The modern way of cel-nav is to pick a point ( lat / lon ), figure what they would have seen at the time of the sextant sight and then compare what they figured to what they did see and figure how big the difference is.  The difference is called the intercept - you move from the assumed lat / lon the distance and direction of the intercept to a new point and say you should be somewhere along a line that includes the new point ( called a line of position )

    The assumed position can be anywhere but is better if it is close to where you are.  There was a thread on NavList a few years back about finding a position without a good AP.  From a assumed point in the middle of the USA, I figured the person was on the west coast - then from an AP in California I figured North west.  My third and last try I used the middle of Washington to get the persion's position in a neighborhood in Seatle.

    I hope this helps and welcom aboard.

    John H.

       
    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