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
    Re: Davis MK 3 Improved
    From: Greg Rudzinski
    Date: 2016 Apr 2, 11:28 -0700

    Performance conclusions of the Davis MK 3 sextant:

    1. Lack of a scope limits use to bright stars, planets, Moon, and Sun.

    2. Only a 2' vernier scale precision on the index arm.

    3. Horizon mirror has no means to adjust out side error. The fixed horizon mirror side error requires making a correction table through the arc. 

    4. Index error must be checked before and after each observation.

    In spite of the above instrument limitations it is still possible to obtain +/- 3' accuracy which makes this ($40 new) plastic sextant a good value for small craft cruiser looking to back-up the GPS. The next post will review the Ebbco Special which is the next step in plastic sextants for the value navigator. 

    Greg Rudzinski

    From: Greg Rudzinski
    Date: 2016 Mar 28, 12:51 -0700

    The Davis MK 3 plastic sextant can be improved by adding solar film filters for index mirror shading and sight tube shading (see image). Solar film shading the sight tube is of big help when determining index error by direct Sun observation vs. natural horizon. Solar film shading the index mirror will show a sharper Sun image than the stock shades.

    Improve Davis MK 3 accuracy by recording arc error through the arc every 10°. Intercepts for observations made from a GPS position will serve as a good enough quick arc error to start with. For better arc error determination use a metal sextant as a standard to compare on simultaneous observations. An assisting fellow navigator is recommended. Otherwise a quick swap between sextants has to be done. Then there are lunar distances and star to star distances if time permits.

    Greg Rudzinski



    Attached 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