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
    Name or NavList Code:
    Re: Haversine scales on slide rules
    From: Brian Walton
    Date: 2024 May 31, 19:08 -0700


    Thank you. I was aware of your and others' brilliant emulators. It would be nice to see if a real ( plastic) 10" rule would work.

    Some years ago, whilst concentrating on reducing a sight at sea, using the procedure probably used by my great-grandfather (time sight) I assembled some of the equipment I used.  You can see a home-made paper sliderule, on which I have added a crude haversine scale. My purpose was not to calculate, but to check that various values I was adding up, were in the right range, at the intermediate stages. You can see that I made various errors and corrections en-route.

    The paper sliderule served its purpose. There is a world of difference in solo sight reduction at sea whilst keeping a close eye on the boat, and doing it in your computer room at home! I am quite incapable of tabulating and adding up rows of figures, and getting it right first time, whilst also hands-on sailing or flying.

    I also worry about the achievable accuracy with a 10" sliderule, as with tha accuracy of Robin Stuart's hand-drawn graphical method. I say this, because Bygrave needed spiral scale lengths of 30 odd feet (30') to get within one minute/mile. No good, a sextant reading in minutes of arc, if the Hc is miles out.

    Somewhere on the net I have found a Bygrave emulator. I have experienced the practicality of using a Bygrave solo in a biplane. It works, but I was vulnerable to making a big splash. Don't do that anymore.


    Browse Files

    Drop Files


    What is NavList?

    Get a NavList ID Code

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.

    Retrieve a NavList ID Code

    Enter the email address associated with your NavList messages. Your NavList code will be emailed to you immediately.

    Email Settings

    NavList ID 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