NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Santa Barbara 2016: Venus sight
From: Stan K
Date: 2016 Dec 19, 12:28 -0500
From: Stan K
Date: 2016 Dec 19, 12:28 -0500
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
