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: Lunar Distance Puzzle
    From: George Brandenburg
    Date: 2011 Aug 22, 16:12 -0700

    Dear Herbert (and Dave),

    Thank you for the excellent "counter example" (below) and the idea of thinking
    about the three lunar distances in pairs. Mea Culpa! If there is only parallax
    of the moon at work and the three stars are fixed it is clear that the third lunar
    distance equation contribues nothing to the problem. We are talking about
    measured distances from fixed points on a two-dim surface, and two of these
    determine an intersection (the moon's apparent position) uniquely without
    any need of the third. And this is independent of GMT.

    So as you have said all along the only hope that the three lunar distance
    equations (in three unknowns) are independent and solvable is to include
    refraction in the problem. Even though refraction is a small correction
    (usually) with respect to parallax for the moon, it also perturbs the positions
    of the three stars in a GMT dependent fashion. Presumably this means
    that adding the third lunar distance can lead to a unique solution for
    lat, long, and GMT. But I certainly can't prove it...


    >On 2011-08-21, Herbert P wrote:
    >Amy, Bob and Jim have together 15 candies. Amy and Bob together have 9.
    >Can you tell me how many candies each child has? Oops, you need a third
    >equation. Jim has 6. Can you tell me now?

    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

    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