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: Fix by equal altitude sights around local apparent noon
    From: Geoffrey Kolbe
    Date: 2009 Oct 13, 21:35 +0100

    In [NavList 10109) John Huth wrote
    
    >For my class, I made a rudimentary quadrant, where the angular scale
    >came from successively bisecting angles to get 64 divisions.   I'm
    >not claiming great accuracy with this, perhaps 30 arc-minutes at
    >best.    I measured the sun's altitude multiple times when it was
    >rising, during meridian passage (for latitude) and then when it was
    >setting.  In terms of getting the LAN, the midpoint of the rising
    >curve and the setting curve turned out to be reasonably accurate,
    >given how rudimentary my quadrant was.   I got to within 20
    >arc-minutes of my longitude (which might not sound like anything
    >great to people accustomed to sextants).
    >
    >Obviously this doesn't work for a moving vessel, but I found it
    >interesting that a crude instrument, coupled with a watch could do a
    >reasonable job in determining longitude.
    >
    >  John Huth
    
    It may be of interest that the method of equal altitudes is probably
    the most precise method of determining a position using a "portable"
    optical device.
    
    The device - called a precision astrolabe in Europe and an
    'equiangulator' in the United States - is quite simple. A telescope,
    a beam splitter and a pool of mercury. By noting the elapsed time
    between the moments when the reflected and direct image of a given
    celestial object were seen to coincide in the eyepiece, it was
    possible to determine position to great accuracy
    
    See, for example, http://www.aggregat456.com/2006/07/geodet.html for
    more information.
    
    Geoffrey Kolbe
    
    
    --~--~---------~--~----~------------~-------~--~----~
    NavList message boards: www.fer3.com/arc
    Or post by email to: NavList@fer3.com
    To unsubscribe, email NavList+unsubscribe@fer3.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