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: Basics of computing sunrise/sunset
    From: Frank Reed
    Date: 2009 Jun 18, 20:21 -0700

    You wrote:
    "If you want to work it out right down to the second of arc of where you are
    and second of time then you must consult refraction tables and work your dip
    out carefully."
    Of course, it's quite pointless to work out sunrise/set times to the nearest 
    second. The refraction at the horizon is variable, as is the refraction "of" 
    the horizon (variable dip). And there's simply no way to predict what that 
    variability will be. The nearest minute, maybe the nearest quarter of a 
    minute, is really about as good as it gets.
    It's interesting, well a little interesting..., that sunrise and sunset times 
    have become standardized calculations with little reference to reality for 
    the majority of people. The same calculation is used for inland locations as 
    for locations with a sea horizon. What does it mean when the standardized 
    calculated time of sunrise is 08:30, e.g., if you're living in a mountain 
    Navigation List archive: www.fer3.com/arc
    To post, email 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