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: determination of longitude and the prime vertical
    From: Bill B
    Date: 2007 Apr 13, 02:58 -0400

    > From: "George Huxtable" 
    
    > 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'.
    
    Agreed. Checked and triple checked, those are the numbers on the site.  As
    always, jump into cyberspace and determine if there is the oft-present typo
    in my post.  Omar is either brilliant and out of step with common thought,
    or wrong by common wisdom. The errors in the Star Finder numbers can be
    traced back to the values in his almanac (please check).  Hence my warning.
    I wish I could be more specific, but given my random use, I find it hit or
    miss vs. the N.A.
    
    If I recall, there was a caution years ago about a site that was currently
    accurate, but historically in error.  I cannot recall if Omar's site was the
    subject.
    >
    > 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.
    
    Same year, same month, same star. I can only dream of playing on the level
    you work on.  I've no explanation for how an almanac and program I cannot
    even fathom authoring is off by that amount.
    
    CYA
    
    On a personal/legal note, as a beginner with a cardboard sextant and 229
    tables Omar's site was both free and a sanity check.  God bless.  For all
    practical small craft cel nav purposes his software is a bargain and equal
    to the task in real-world situations.  I have no cause to disrespect his
    work product.  I would caution for precise usage, cross checking with other
    sources would be prudent as always.
    
    Bill
    
    
    --~--~---------~--~----~------------~-------~--~----~
    To post to this group, send email to NavList@fer3.com
    To unsubscribe, send email to NavList-unsubscribe@fer3.com
    -~----------~----~----~----~------~----~------~--~---
    
    

       
    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