Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Altitudes, close to 90
    From: Bill B
    Date: 2004 Dec 1, 19:30 -0500

    > Sure. Bauer writes:
    > "Swinging an arc is also called rocking the sextant and simply means
    > rotating the instrument from side to side around the line of sight to the
    > horizon."
    > And that's not right, but it's a very common error. When this is done
    > correctly, the axis of rotation is about the line of sight to the object in
    > the sky. If the object is nearly straight up, that means you have to rotate
    > instrument around a nearly vertical axis.
    Thank you Frank,
    It seems to me that once seen it is simple, but putting the technique into
    words is challenging.  Especially if the motion being described is in error
    to begin with.   Somehow I had envisioned a situation where top dead
    center of the sextant was affixed to a conceptual ball joint, and the
    sextant was swung left to right like a pendulum.
    If I understand you in the case of a body near zenith the sextant would be
    swung left to right as though it were fixed to ball joints near top dead
    center and and bottom center.
    I am assuming the axis of rotation (along the line of sight to the body)
    would pass through the index mirror.  Is that correct?

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    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 Settings

    Posting Code:

    Custom Index

    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