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: Dip Variation by Theodolite
    From: Bruce J. Pennino
    Date: 2014 Jan 3, 17:09 -0500
    I just check the specifications for the total station: magnification = 30x ; field of view 1 degree 20 minutes. Does this make it to easy? 
    Frank, by the way , I'm glad you remembered that we made the vertical angle exactly 90 degrees. Not in my notes.

    ----- Original Message -----
    From: Frank Reed
    Sent: Friday, January 03, 2014 4:33 PM
    Subject: [NavList] Re: Dip Variation by Theodolite

    Many of you may recall that Bruce Pennino brought his total station (theodolite) to Beavertail Point at the southern end of Conanicut Island a couple of months ago. We experimented with measuring height of eye and he demonstrated his direct measurements of dip. A large car carrier was headed in, getting ready to sail up into Narragansett Bay, and anchored briefly south of Newport. Bruce aimed the theodolite at the ship for a better look, and I held my phone up to the ocular to snap a few photos. Smartphone cameras take very nice images by this direct eyepiece projection technique since they have infinite focus by design. Here's a photo showing the big ship and the crosshairs. Given that the horizontal crosshair line sits on the true horizon, what can you figure out about this ship and other aspects of the observation? How far away is the ship? How big is it? Do you need to know height of eye (about thirty feet) to figure that out from this photo?

    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

    Attached File:

    (theodoship.jpg: Open and save)

    View and reply to this message: http://fer3.com/arc/m2.aspx?i=126156

    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