Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Name or NavList Code:
    Index error test with Davis whole horizon mirror
    From: Erik Rosen
    Date: 2023 Sep 14, 06:13 -0700

    I have a Davis 25 sextant with a "whole horizon mirror". I think that's what they call it. It's not split into a mirrored side and a clear side. 

    What's the best way to measure the index error on this sextant? The usual ocean horizon test that I find in books doesn't work well. It's diffiult to see two horizons when they are close together. The Sun test doesn't work since the shades in the horizon direction aren't dark or dense enough. I need something that I can test easily, on the spot as I'm taking sights. Any ideas?

    Erik Rosen

    Browse Files

    Drop Files


    What is NavList?

    Get a NavList ID Code

    (please, no nicknames or handles)
    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 Settings

    NavList ID Code:

    Custom Index

    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