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: Using a slide rule for celnav
    From: Gary LaPook
    Date: 2014 Jan 21, 00:19 -0800
    Good question. I only became interested in it after reading Chichester's book about crossing the Tasman Sea in 1931 utilizing the Bygrave to find tow small "must find" islands along the way. (I have this book on my computer and can send it to anybody who wants a copy, it is a great read.)
    I don't know how much they cost and then there is the problem with them loosing the friction between the cylinders necessary to keep them from sliding after being set. Those of us who have made copies of the cylindrical Bygrave know how difficult it is to get everything right. Fortunately, it is a lot easier with the Flat Bygrave. ( https://sites.google.com/site/fredienoonan/other-flight-navigation-information/modern-bygrave-slide-rule ) The Germans made a lot of their copies and used them on ships and submarines and they included a locking mechanism for the tubes.


    From: Francis Upchurch <francisupchurch@gmail.com>
    To: garylapook@pacbell.net
    Sent: Monday, January 20, 2014 11:23 PM
    Subject: [NavList] Re: Using a slide rule for celnav

    I use a homemade replica Bygrave for most of my LOPs, great circles and the second half of my lunar clearances (still can't do the first bit!see earlier postings. Any maths wizards please help!). Generally get within 1' of a calculator result and nearly as quick. I use a replica cylindrical Fuller for general cosine formulae and the lunar first bit (cosine formula). The Fuller is twice the size of the Byrave with vulnerable brass cursers and I've nearly finished a miniaturized version (similar size to Bygrave),with robust curser that is just as accurate (albeit with the aid of magnifying glasses to see the reduced scales.)This gives 4-7 decimal place accuracy with any formulae but a bit slower than the Bygrave.I've never tried using a 10" linear for cel nav. Very interested to hear it works better with Bygrave formulae.I will now try the mini Fuller using the Bygrave formulae. From what Gary has been saying, this may be even more accurate?
    I can send details in a couple of weeks on request.
    Another unanswered question, perhaps to Gary? The Bygrave is faster and just as accurate as Air Almanac in my experience, second only to modern calculators. why was it never standard issue during WW2? Only a few top RAF navigators used it and Chichester does not mention it in his RAF nav instruction books.
    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
    View and reply to this message: http://fer3.com/arc/m2.aspx?i=126594

    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