A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2014 Jul 31, 15:45 -0700
Don wrote: "Wouldn't these tables be for the Paris meridian, at about 2°20' East of Greenwich?"
And Gary replied: "Oui, mais certainement. "
Yep! I think you'll find that they are listed for hours of Paris Apparent Time. So when the table lists the Sun-Moon lunar distance for "midi" on the 1st of Brumaire, that's a real "midi", local apparent noon. The lunar distance is correct, up to the limits of their calculational skill, for the instant when the Sun's center is crossing the meridian of the Paris Observatory. My online app will happily provide the lunar distances for hours of Greenwich Apparent Time (as was standard in the early almanacs, instead of GMT), but you'll have to do a short calculation to adjust them to the longitude of Paris.