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
    Name or NavList Code:
    Email:
       
    Reply
    Re: determination of longitude and the prime vertical
    From: George Huxtable
    Date: 2007 Apr 13, 00:08 +0100

    Bill wrote-
    |
    | It is quite possible this site's program
    | (http://www.tecepe.com.br/cgi-win/cgiasvis.exe by Omar Reis) may be off on
    | GHA, LHA etc, by more than a rounding error in it's Navigator Star Finder
    | section.  It depends on the body.  Other areas of concern are stated RA's
    of
    | bodies converted to SHA and compared to the N.A.  Also note the
    declinations
    | given for Polaris for May: Site 89d 16!7, N.A. 89d 17!8.
    
    Comment from George-
    
    Well, if so, that's a bit of a worry. It's an unacceptable discrepancy, of
    1.1 arc-minute, in the prediction of Polaris' declination! My own pocket
    calculator gives for 1 May 07, 89 deg 17.7', which is close enough to the
    Nautical almanac figure that Bill gives of 89 deg 17.8'.
    
    So what's the origin of that erroneous declination of 89 deg 16.7' in the
    Omar Reis program, I wonder? It seems too big to have come from neglecting
    aberration, which can only shift Polaris dec from its mid-value by about
    0.3' or so, either way; not even when nutation is added. Is there something
    wrong with its allowance for pression, perhaps? I ask Bill to double-check,
    please, to make sure that he is comparing predictions for the same year. If
    Polaris is indeed that far out, can any predictions from that site be
    trusted, for precise work? I wonder if others have comments about that.
    
    George.
    
    contact George Huxtable at george@huxtable.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
    --~--~---------~--~----~------------~-------~--~----~
    To post to this group, send email to NavList@fer3.com
    To , send email to NavList-@fer3.com
    -~----------~----~----~----~------~----~------~--~---
    
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Get a NavList ID Code

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.

    Retrieve a NavList ID Code

    Enter the email address associated with your NavList messages. Your NavList code will be emailed to you immediately.
    Email:

    Email Settings

    NavList ID 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