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: What should I expect for a land based sight accuracy
    From: Alan S
    Date: 2014 Jan 9, 15:47 -0800


    Regarding accuracy of "land locked sextant shots",my own experience might be illustrative of what can be expected, though possibly not.

    I'm using an Astra 111B, with the factory telescope, 3.5 x 40mm and a Davis Artificial Horizon, essentially a dish of water, with sun and wind shields.

    I do AM and PM sun shots, 4 -5 hours apart, in the parking area of the apartment complex where we reside, and compare my calculated position fix with GPS coordinates.

    My calculated fix is usually inside 3 NM, sometimes inside 2 NM of GPS coordinates, sextant sights having been reduced and the LOP's plotted. I use USPS Sight Reduction Form and their CLS plotting sheet, which covers 1 degree lat x 1 degree long. Since I'm standing in essentially the same place for the sextant shots, the limitations of the CLS plotting sheet are not a problem.

    Looking at one such plot,the "a" distance for AM shot was 0.6 NM Away, PM "a" distance was 1.7 NM Toward. Plotting the LOP's gave me a calculated fix 1.8 NM, scaled with dividers, South-West of GPS coordinates.

    Hope the foregoing is of some help to you.

    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com

    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