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
    Re: Index Error - Real vs. Artificial Horizon
    From: Bill B
    Date: 2013 Feb 28, 17:05 -0500

    On 2/28/2013 4:32 PM, Paul Fithian wrote:
    > For example, if I adjust the horizon mirror so that a near (5' away)
    > horizontal line matches up through the glass and the mirror images,
    > these images don't line up when I view a horizontal line that is several
    > hundred feet away.
    
    To give you a few parallax examples:
    
    Lets assume the distance between between the centers of the index mirror
    and horizon glass/mirror is 3 inches. (This is probably not static and
    depends on sextant geometry and front vs. rear silvered index mirror.)
    
    At 5' (60") using tangent the angle is 2d 51' 45"
    At 300 feet 0d 02' 52"
    At 1 nautical mile it is 0d 0' 9"
    
    For your immediate needs and the error in the entire system, 1 nm is
    probably sufficient, but not optimal.
    
    Bill B
    
    
    
    

       
    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