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Thanks Sean,

I will send them a note pointing the inconsistent definitions of astronomical twilight.

Best,

Rob

-----Original Message-----
From: NavList@navlist.net [mailto:NavList@navlist.net] 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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