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: Sextant observations in the Chesapeake Bay
    From: David Iwancio
    Date: 2022 Aug 1, 18:57 -0700

    For taking individual practice sights this seems reasonable (or it might be interesting to work "backwards" to determine the distance to land), but for a round of sights to get a celestial fix you'll end up with a (probably insignificant) bias towards the nearer shore.

    One question is how this error compares to how much dip varies in non-standard conditions.  One paper I found at https://journals.lib.unb.ca/index.php/ihr/article/view/27073 suggests that it can vary by as much as ~1.0' for a 2 °C difference between air and water temperature.

    On a side note, for Bowditch tables 12 & 14 the β0 term appears to be (1 - Re/Rr) where Re is the radius of the earth and Rr is the radius of curvature of a refracted ray of light.  I came to this conclusion from looking at https://www.mathscinotes.com/2013/08/distance-to-the-horizon-assuming-refraction/

       
    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