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 checks with laser and without
    From: Alexandre Eremenko
    Date: 2007 Jan 3, 21:37 -0500

    
    Fred,
    
    > Have you tried introducing a bit of side error?
    
    I always have a little bit, not because I introduce it
    but because my SNO just does not hold this adjustment.
    (And I've heard on this list that this is a problem
    with other SNO's as well). It always looks less than
    1 minute;
    when it is more I adjust it, say every other month.
    
    But it does not help me much with stars index checks.
    The stars I see are not exactly points, and brighter
    ones look bigger. This could be a telescope problem
    but more likely my vision problem.
    
    Anyway, I am quite confident with Sun checks by now,
    the results I cited in my previous message are well
    reproducible and typical. And unlike the side error,
    the sextant seems to hold the index error unchanged for
    years. Now I double checked it with lasers.
    
    Speaking of my main business with this sextant,
    the Lunars, I am still at loss why my results are
    sometimes very good and sometimes very bad (for the Lunars).
    I am pretty sure that this is a sextant problem
    (not my vision) but I still cannot find where exactly
    it is. Frank had my sextant for checking for few weeks
    but he reported only one observation (which was good),
    so his checks did not give much.
    He gave me one advise though which seemed to help a lot
    first (to relax one little screw to ease the movement of
    the worm) but then, with more tests, I found that the
    problem did not disappear.
    Very many observations show that the sextant can be in
    two states: sometimes it measures a Lunar perfectly
    (to 0.1' or 0.2' and sigma is between 0.1 or 0.2
    in a series of 10-12), and sometimes I have errors
    of 0.4 and even 0.8, always overshots, no matter what
    I measure, a near limb or a far limb.
    And the errors almost do not correlate with measured
    angles. So this is not a result of an arc defect.
    This looks like some non-rigidity, some part of
    the sextant which should be rigid actually moves.
    And what part, I don't
    understand. The only thing I can feel is a very slight
    lateral motion of the sextant arm. But they say that this is
    unavoidable, even in the best sextants. This does not
    seem to have any effect: see my checks of the IC
    hand up and hand down.
    
    Alex.
    
    
    
    
    --~--~---------~--~----~------------~-------~--~----~
    To post to this group, send email to NavList@fer3.com
    To , send email to NavList-@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