A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Antoine Couëtte
Date: 2016 Sep 25, 03:04 -0700
Thank you very much for your last reply which clarifies the requested last points for me. BTW, could you not perform the Moon "center of mass to center of figure correction" more accurately now since the most recent modern Theories also give Libration angles. Yes?
To all readers: it is interesting to observe that through 2 distinct "Modern Lunars" software 100% independently developed over the new and unpublished then idea of using "Sextant Refracted Distances" instead of the Classical "Cleared Distances" we get so close results. And as earlier surmised the main appreciable differences between our results just come from our different Refraction Models.
As a concluding summary:
Modern computing power enables to tackle Lunars [much] better than the Classical Methods could and can [ever] do it. The Sextant "Observed Refracted Distances" have now become the main computation variables and benchmarks. No longer need to use the Classical [and formerly unavoidable] intermediate variables - i.e. the "Cleared Distances" - which sometimes vary with Time (UT1) in a manner totally different from their Observed Sextant Distances counterparts.
"Modern Lunars" Software also enable computing the observed sextant distances first derivatives with respect to UT1 . These first derivatives are greatly dependent of their local environment. Accurately knowing such first derivatives immediately indicates the accuracy which can be expected from a given Lunar. Classical Methods do not give [immediate] access to this essential information.
Nothing here to downgrade Classical Lunars which have been a Celestial Navigation Legend over Centuries. My hat down to Maskelyne, Mayer and the French Astronomers on the shoulders of whom they stood, and to the immense Newton ... ***. Classical Lunars will definitely continue attracting many enthusiast Lunarians here.
Simply to show that modern computation tools can bring additional and quite valuable insights on some Lunars characteristics - i.e. their actual expected accuracy and therefore their real value in terms of reliability - which had to be set aside in the past because of the lack of adequate computing power then.
Had they known then what we can accurately know to-day about the actual Longitude accuracies they could expect from their Lunars - again, so much dependent on their local environments - maybe some of our Forebear Navigators might have been more cautious then.
Hence this concludes my Contribution on "Modern Lunars".
Antoine M. Couëtte
CDR (R) French Navy
(Active) A343-345 Pilot
*** from "About Lunars" by our [very] much regretted George Huxtable who was the first one actually whom I personally contacted about Lunars.