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: Time of meridian passage accuracy
    From: Peter Hakel
    Date: 2009 Sep 25, 15:19 -0700


    From: George Huxtable <george{at}hux.me.uk>

    On the 29th April, the Sun's declination is increasing
    (Northward) by about 0.8 arc-minutes per hour.

    ==============================================================================


    If we define:

    d: hourly rate of change of Sun's declination in arcminutes
    D: number of days elapsed during the current year
    a: "phase angle" ( a~0 at winter solstice, a~90 at vernal equinox, etc. )

    a = {D+10} / 365 * 360 degrees

    then the following approximate expression for "d" seems to work well enough:

    d = 60 * 23.45 * SIN(a) * ( 360 / 365 ) / 24 * ( Pi / 180 )

    For April 29 we have D=118 and hence d=0.8' per hour, just as George stated above.


    Peter Hakel



    --~--~---------~--~----~------------~-------~--~----~
    NavList message boards: www.fer3.com/arc
    Or post by email to: NavList@fer3.com
    To unsubscribe, email 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