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    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.
    
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