NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lunars: Weymouth log (revised)
From: Frank Reed CT
Date: 2004 Dec 8, 18:32 EST
From: Frank Reed CT
Date: 2004 Dec 8, 18:32 EST
Alex, you wrote:
"You are saying that they usually did not correct
the DR position for the lunars except in one case.
Did they correct their DR position for observed
latitudes? And how? Just shifting the DR position
along the meridian?"
the DR position for the lunars except in one case.
Did they correct their DR position for observed
latitudes? And how? Just shifting the DR position
along the meridian?"
It seems to have been moderately unusual to correct the DR longitude based
on a lunar longitude, but when the DR lon or chronometer lon was way out of line
then they did it. Sometimes two DR longitudes would be calculated: one based on
the last land departure and another based on the best recent lunar
observation. But they always reset the DR when known land was sighted. In
the Atlantic, there were a number of islands that navigators sailed towards
specifically in order to use them as new departures. Trinidade and Martin Vas
off the coast of Brazil are examples.
Except for one very early logbook that I've read, the latitude that's
recorded is usually "Obs Lon" and in every case where it's mentioned, it's a
noon observation of the Sun. The stars were rarely used at sea in the 19th
century. Celestial navigation was a daytime activity.
The DR latitude seems to have been recorded only in bad
weather.
Frank R
[ ] Mystic, Connecticut
[X] Chicago, Illinois
[ ] Mystic, Connecticut
[X] Chicago, Illinois