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
    AN-5851-1 Repair
    From: Dave Harwood
    Date: 2011 Nov 25, 03:51 -0800

    Hello everyone,

    I recently purchased a Navy Mark V AN-5851-1 (A-14) sextant and was pleased to find it in remarkably good condition upon arrival. A bubble is easily formed and removed. The averaging mechanism runs precisely two minutes and is accurate to within 1’ or less. I have only a few minor complaints.

    First, I took it out for a few sights and was disappointed to find it was reading significantly off. Aligning the bubble on the sea horizon and correcting for dip, I estimated an index error of -19’. After a day of sun sights at 30 minute intervals, I found the mean, median and standard deviation of my intercepts from a known location to be -17.3’, -17.6’ and 2.0’ respectively. Correcting my sights for an index error of -17’ placed my position within two miles of my known location.

    This index error seems rather significant. Would it be worthwhile to make an adjustment to the sextant or just mathematically correct the sights with this index error? If I were to make this adjustment, how is this done? I’ve discovered some adjustment screws on the backside of the index prism. I’ve decided not to mess with these until I am sure I know what I’m doing.

    Second, the shutter that should block the view as the timer runs down does not seem to be working. It is only slightly darker when the timer stops. It seems that maybe the shutter is sticking and only partially blocking the view. Is this worth a tear down to repair, or should I just live with it?

    I have successfully restored a few A-10A’s and a British Mark IX. I just don’t have any teardown info for this sextant, so I am a little leery of opening this one up since it is in 95% working order.

    Any advice from the experts of NavList would be greatly appreciated!

    Dave Harwood

    ----------------------------------------------------------------
    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?

    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