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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Santa Barbara 2016: Venus sight
From: Brad Morris
Date: 2016 Dec 19, 13:45 -0500
From: Brad Morris
Date: 2016 Dec 19, 13:45 -0500
'Astron' disagrees with Dutton, which has all three periods beginning (ending) simultaneously with the suns orb at setting (rising).
On Dec 19, 2016 12:40 PM, "Stan K" <NoReply_StanK@fer3.com> wrote:
Peter,
I've been trying to send this privately, both on and off NavList, but the messages keep getting returned. I thought you might have changed you address because of the Yahoo hack, but your messages seem to be coming from the same old address.
Anyway, I have a question about the way Astron defines twilights. All the definitions of twilight, whether civil or nautical (or astronomical) that I can find involve the sun, rise or set. Morning twilight starts at the start of AM nautical/civil twilight and ends at sunrise. Evening twilight starts at sunset and ends at the end of civil/nautical twilight. Astron seems to define AM twilight as starting from the start of AM nautical twilight and ending at the start of AM civil twilight; PM twilight starts at the end of PM civil twilight and ends at the end of PM nautical twilight.
If there is a reference that defines twilights this way, please let me know what it is.
Stan
