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: Time of meridian passage accuracy
    From: Douglas Denny
    Date: 2009 Sep 25, 23:51 -0700

    I do not believe I have missed the point. I believe you have.
    I am aware of the changing declination of the Sun - it is changing constantly, 
    hence a meridian passage curve such as the one I gave is actually skewed - in 
    theory.  The question is: to what extent?  Answer - very small as to be of no 
    practical concern to practical navigators.
    The change in declination per DAY, as you say is only 0.8 minutes of arc - 
    which applied as an altitude correction it is negligable in practical 
    The differences between actual (appareent) max Altitude and true Mer passage 
    of the Sun are so small as to be negligable if max altitude is calculated 
    near to the apparent Mer Passage... and if not so, why does the Nautical 
    Almanac persist in publishing the Sun's Mer Passage each day so navigators 
    can use Max altitude?
    There is a vast difference between practical navigation and theoretical astronomy.
    That is the point which you have academically and pedantically missed.
    Douglas Denny.
    Chichester. England.
    Douglas Denny has missed the point. The nearness of his observation point to
    Greenwich has nothing to do with it. The time correction, due to changing
    declination, as the same the whole world over, at the same latitude and
    His calculated time of Meridian Passage may well be correct. But he isn't
    observing Meridian Passage, when the Sun is due South. He is observing
    maximum altitude, the peak of the curve, which is subtly different.
    NavList message boards: www.fer3.com/arc
    Or post by email to: NavList@fer3.com
    To unsubscribe, email NavList-unsubscribe@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