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: Definition of the twilight intervals
    From: Robert H. van Gent
    Date: 2015 Aug 26, 14:27 +0000

    Thanks Sean,
    
    I will send them a note pointing the inconsistent definitions of astronomical twilight.
    
    Best,
    
    Rob
    
    -----Original Message-----
    From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Sean C
    Sent: dinsdag 25 augustus 2015 18:17
    To: Gent, R.H. van (Rob)
    Subject: [NavList] Re: Definition of the twilight intervals
    
     [BEGIN QUOTE]
    However, modern editions of Bowditch's "The American Practical Navigator" do not seem 
    to be consistent with the definition of astronomical twilight.
    
    In the 2002 online bicentennial edition (the latest to which I have easy access), 
    astronomical twilight is defined as the interval between -0 degr 50 arcmin 
    and -18 degr (table 1516 on p. 227) while the Glossary of Marine Navigation 
    in the same publication defines it as the interval between -12 degr and -18 
    degr (p. 725).
    
    Whom should one contact to point out this inconsistency?
    
    Rob van Gent[END QUOTE]
     
    Rob,
     
    Apologies for replying to this so long after you posted it, but I was just browsing 
    through my copy of Bowditch, saw the table you were referring to and was 
    reminded of your question. Bowditch is prepared and published by the National 
    Geospatial-Intlligence Agency (Formerly the National Imagery and Mapping 
    Agency). Their  [LINK: http://www.nga.mil] website gives their mailing 
    address as:
     
    National Geospatial-Intelligence Agency
    Office of Corporate Communications
    Public Affairs Branch, MS N73-OCCAE
    7500 GEOINT Drive
    Springfield, Virginia 22150-7500
     
    ...and their email address is:  [LINK: mailto:publicaffairs{at}nga.mil] publicaffairs 
    -at- nga.mil. Hope that helps.
     
    Regards,
    Sean C.
    
    [PLAIN TEXT VERSION OF MESSAGE AUTO-GENERATED. ORIGINAL MAY INCLUDE MORE CONTENT]
    ----------------------------------------------------------------
    NavList message boards and member settings: www.fer3.com/NavList Members may 
    optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com
    ----------------------------------------------------------------
    
    
    
    : 
    http://fer3.com/arc/m2.aspx/Definition-twilight-intervals-SeanC-aug-2015-g32543
    
    
    
    
    

       
    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