NavList:

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?"

 

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.