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
    Re: Time sight primer
    From: Chris Mitchell
    Date: 2019 Sep 27, 06:27 -0700

    Thanks to everyone who have chimed in on this topic, and provided some clarification to the issue.

    Frank, when I asked "would it be safe to say that this method of finding longitude and local apparent time was replaced with by more modern longitude by chronometer method and UTC?" I should have been more specific. I realize now that there is more than one “version” of a time sight, this method that I have been asking about relies on table XXV in the older versions of Bowditch. The method that I am familiar with uses the formula: cosP = (cosZD – sinLat * sin Dec) / (cos Lat * cos Dec). In the end, both methods accomplish the same thing, I was just wondering if this newer formula method would have superseded the older Bowditch method, however the Bowditch method with its tables would definately be easier if you never had a scientific calculator to comput the formula. Are there any other "versions" of time sights besides the two mentioned perviously (Bowditch tables & formula)? Also, with the implementation of time zones I assume that keeping local apparent time became a thing of the past on ships. The only time I hear it mentioned onboard now is when referencing local apparent noon for a noon sight.


    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    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 Settings

    Posting 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