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: Sight Reduction by the Cosine Haversine Method
    From: George Huxtable
    Date: 2004 Oct 7, 23:22 +0100

    I was responsible for diverting this discussion into Ptolemy's grasp of
    trig. around AD 150. So apologies to anyone who is outraged by taking
    matters so far away from the practical problems of navigation.
    Herbert Prinz responded.
    >Trying hard to give the appearance that what we are discussing here has
    >to do with navigation, I shall mention in passing the name of Cotter. (I know,
    >George, that you maintain this list...)
    >In A History etc., p.16 he writes that "Ptolemy had the theorem
    >    "sin(A+B) = sin(A)cos(B) + cos(A)sin(B)
    >"This theorem is usually known as Ptolemean Theorem."
    >Now that you have seen the relevant chapter in the Almagest, would you agree
    >with this?
    My perspicacity is less than Herbert rates it. All I have done, so far, is
    to dip into Ptolemy.
    I probably wouldn't recognise "Ptolemy's theorem" if it said "hello" to me.
    Presumably, it would have to be expressed in different terms to the
    equation Cotter gave, as Ptolemy doesn't seem to have cosines, as such,
    within his grasp.
    So I can't answer Herbert's question, but it would be interesting to
    discover his own view of that matter.
    contact George Huxtable by email at george@huxtable.u-net.com, by phone at
    01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
    Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

    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