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: SNO-Ts on eBay with Horizon Mirror Installed Backwards
    From: Bill Morris
    Date: 2012 Apr 1, 16:38 -0700

    Ken

    you wrote:

    >...switching the arm (alidade), or micrometer drum would
    completely negate the original test certificate.<

    I'm not sure I can agree with this. The accuracy of a micrometer sextant resides mainly in the centring of the rack and the division of the teeth. Dismantling a SNO-T cannot disturb these, as the bearing is machined directly into the frame. Periodic pitch errors in the micrometer worm might lead to minor errors of the order of arc seconds distributed around the micrometer drum and they might vary a little from worm to worm, but not I think by an amount that would be of practical importance.

    I cannot see how switching the index arm could affect the instrumental accuracy.

    Most other sextants have the bearing attached as a separate piece to the frame and in general I would say that this ought not to be disturbed, even though it is usually a very close fit in the frame. If it is necessary for some reason to do so, it should be replaced in the same position it occupied before. Otherwise a new centring error may be introduced.

    Bill Morris
    Pukenui
    New Zealand
    ----------------------------------------------------------------
    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com
    ----------------------------------------------------------------

       
    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