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: Perpendicularity
    From: Herbert Prinz
    Date: 2004 Oct 12, 20:05 -0400

    George Huxtable wrote:
    
    > That [my 2nd paragraph] refers to the two-cylinders method of alignment, doesn't
    > it, not the
    > method where you look at the reflected edge of the arc, which is what I was
    > considering. Or have I missed something?
    
    Yes, but further down I deal with the arc, too. It's really the same problem. What
    happens if you have a pair of cylinders that are a little shorter than ideal? Then
    you bring your eye into the plane parallel to the limb passing through these
    cylinders. And if the cylinders are of height zero? Well, then you won't be able to
    do this, because you won't see the "top of the cylinders", i.e. the arc itself. You
    have to cheat and look from above.
    
    So we have 3 cases.
    
    1. The mirror plane is centred on the pivot. Any method works fine, because you can
    look from any vertical angle without getting parallax.
    
    2. The mirror is to the side.
    
    2.a. Using cylinders, look from correct position in proper plane and get no
    parallax.
    
    2.b. No cylinders available, must use arc, tough luck, parallax unavoidable.
    
    Herbert Prinz
    
    
    

       
    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