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
    Ebbco Special with Sight Tube Modification Compared
    From: Greg Rudzinski
    Date: 2016 Apr 13, 20:26 -0700

    Ebay has provided an Ebbco Special plastic sextant at a very reasonable $30. This version of Ebbco has better quality mirrors than the standard model and is the model to get. As expected on older Ebbco's the filters were bad. The best fix is solar film. See this old post on how to do it.

    http://fer3.com/arc/m2.aspx/Ebbco-Sun-Shade-Modification-Rudzinski-sep-2014-g28501

    Another worth while modification is the addition of a sight tube. For this an old mag light was cut down and taped to fit the scope mount. See attached image. Arc error corrections were determined by comparing horizontal angles against a metal sextant then checked at the beach for repeatability. This method seems to work.

    See the attached artificial horizon data that compares the calibrated Ebbco Special against the Cassens & Plath and calibrated Davis MK 3. I made it a fair fight by taking all sights on all sextants with a sight tube. Index errors were checked by x4 or x3 power scope.

    The plastic sextants can get the job done if you put the time in to dial them in. I still prefer and recommend the metal sextants but if weight and space is an issue then plastic may be an acceptable choice aboard a small craft.

    Greg Rudzinski



    File:



    File:



       
    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