NavList:

George H wrote:

"The same question arises, for the Almanacs around 1803. How precisely was the Moon's Right Ascension tabulated, and at what time intervals?"

You can check online at the G.W.Blunt-White library on the Mystic Seaport web site. Or... there is a description of the accuracy levels of the early tables in Sadler's "Man Is Not Lost", which, if I remember correctly, you own.

 

But it doesn't matter. The almanac is not required for clearing any lunar observations for longitude UNLESS you need the longitudes en route (as aboard a ship at sea heading for a destination with a known latitude and longitude). We've discussed this recently. For exploration and mapping where the longitudes en route are not critically necessary, what you need most of all are good observatory observations (e.g. at Greenwich) covering the period of the observations made in the field. This was the fundamental issue that seems to have escaped those early American seekers of longitude.

 

-FER