NavList:

Hello Lars,

Probably [very] first time I work on an Historical Lunar directly from the logbook itself, which is GREAT !!!

I may not and will not claim having any experience here. And as a matter of fact:

Top of this page, I can read:

August 26th, sea account at 3h39m36s P.M. Latitude 24°51'N

and further down, one line before last, by mid-page I can read :

Mean Time at ship 3h41m35s [Chronometer just corrected for rate, see line immediately above]

which obviously pertains to the same "Local Mean Time" (LMT) scale.

From both lines we are to infer that the elapsed time between the last Latitude DR determination at LMT 3h39m36s PM (top of the page) and Lunar time at LMT 03h41m35s [PM] is just 2 minutes (and not 2h10m as earlier stated).

So, yes, there is an error on my behalf : 2 minutes elapsed between the last DR'd Latitude and the lunar itself, vs. 2h10m as previously stated.

Therefore my previous comments on Latitudes are void, while comments on Longitudes should remain unaffected.

Thanks for bringing this point to my attention.

*******

As we all know, at their epoch - from c.1780 until c.1880 - when observing their Latitudes (most often by meridian passages) Navigators were sailing on DR Longitudes, and when solving for their Longitudes through Lunars most often had they to resort to DR Latitudes.

What remains interesting though is that - even probably knowingly for at least some of them - Navigators had all data at hand then to reasonably start navigating by Marcq Saint Hilaire's LOP's, unknown at that time.

Through actually solving for both Longitude and Latitude at the same time through our all too familiar LOP's, modern reprocessing of their Lunars enables to compute the best achievable fixes Navigators of these epochs could have obtained.

Just a curiosity since Lunars have long been dead.

Best Lunarian Regards to you too Lars, and thanks again for your sharp eye.

Kermit

antoine.m.couette@club-internet.fr