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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
19th c Local and Greenwich Time Conventions
From: Ed Popko
Date: 2018 May 15, 05:48 -0700
From: Ed Popko
Date: 2018 May 15, 05:48 -0700
The recent South Pacific thread illustrates a big trap in deciphering 19th century navigation scraps -- what time convention is being used and how to get consistent Greenwich and Local right when computing Longitude.
In time sights, you can usually get the hour angle right and you can figure out if the body is rising or setting. But from there on out, the time convention trap opens up.
Longitude = Greenwich - Local Time be they apparent or mean time.
Is there a consistent way to treat Nautical and Civil Time conventions in time sites and to know which is being used when computing the final Longitude?
Ed Popko
