Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: Lunar Distance Puzzle
    From: UNK
    Date: 2011 Aug 19, 19:56 +0000

    On 2011-08-19 16:22, Frank Reed wrote:
    > In any case, when I thought it through a bit further I got right back
    > to square one. If we limit ourselves to any pair of lunar distances or
    > in my hypothetical case, any pair of stars sitting right on the Moon's
    > limb, the observations uniquely determine the Moon's topocentric
    > position in the sky (well, really there might be two solutions but
    > widely separated so no issue to distinguish them).
    
    Right. Since this is question of geometry and what has been posted
    against it so far are number games where I have neither  seen the
    (intermediate) numbers nor the underlying algorithms, anyone can guess
    which side I am leaning towards.
    
    > But this still leaves us with the problem that the "black box"
    > solutions say otherwise. Clearly Dave W. and Harri and Peter are
    > solving somehow for GMT and position at the same time, but it's highly
    > sensitive to the exact position data and the exact model specifications.
    
    Dave's refraction-free topocentric distances are not even consistent
    with each other to arc second level. Ex falso quodlibet. I have asked
    from which point they are supposedly measured.
    
    Harri used refracted distances and stated that he used the same N.A.
    approximation formula that had presumably been used to generate them.
    His solution, if otherwise correct, is therefore entirely based on
    differential refraction. He concluded that the problem is "doable in
    principal".
    
    Indeed, "in principal", whatever that means.  "In principal",
    Aristarchus found the distance of the sun by measuring its angular
    distance from the moon at half moon. "In principal", Ptolemy was able to
    determine the moment of solstice by observing the shadow of an
    equatorial ring. "In principal", Halley was right to think that one can
    find longitude from compass variation.
    
    Herbert
    
    
    
    
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    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:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    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