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: Moon Parallax, Math Trivia (was Re: venus)
    From: Frank Reed CT
    Date: 2004 Oct 20, 18:35 EDT
    Herbert P wrote:
    "I believe you are mistaken. There is no resemblance to Kepler's
    equation. The characteristic feature of the latter is that the variable
    E (eccentric anomaly) appears as a term E as well as a term sin E,
    making it impossible to express E as explicit function of the mean
    anomaly. "

    Here's the direct equation for the calculation of the true altitude from the observed altitude and the horizontal parallax:
      TA = OA - HP cos TA .
    OK? You agree, I hope, that this bears a very STRONG resemblance to Kepler's equation. Now invert it. Solve for TA. Can't be done in "closed form", right? See what I mean now?? If you solve this iteratively for TA to, say, one part in a million and then compare with the Arctan solution, you will get slightly different results. They are not inverses. They solve slightly different mathematical problems. That's the "trivia" I was getting at.

    Frank R
    [ ] Mystic, Connecticut
    [X] Chicago, Illinois
    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)