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: Shadow sights for longitude
    From: Mark Knudsen
    Date: 2018 Jan 12, 19:15 -0600
    I am familiar with pin holed cameras have taken  many photos with them. I could use a little more detail for the use of a ball  .it sounds  interesting  I am very interested in simplified practical navagation methods on land  thanks  mark

    On Jan 12, 2018 4:31 PM, "David Fleming" <NoReply_Fleming@fer3.com> wrote:

    Increaseing shadow length will not improve the accuracy.  As has been noted the accuracy is limited by the sun not being a point source of light.  A sextant  or the observers eye in the case of a sextan sight taken without a telescope produces an image of the sun atop the horizon, so that the angle to a specific point on the sun is measured.

    If you wish to achieve such accuracy using shadows, then build a pin hole camera. And position a small ball in the center of the image.  Then the angle of the ray from the pinhole to the ball relative to the horzontal will more accurately duplicate a sextant height measurement.

    The reference to longitude is only due to John's taking prime vertical sights.  Apply to meridian transit sights and you have latitude.


    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