NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Antoine Couëtte
Date: 2022 Oct 14, 02:24 -0700
Jeremy, you just shared your experience about Moon sights : and the moon in general; I always have a low confidence in, just based on experience.
This is worth setting up a new thread here since we have here an interesting opportunity to discuss together the following subject on NavList : what are the possibile reasons why Lady Moon has been considered with caution if not reluctance when it comes to LOP's ?
From own experience - eralier addressed here - I can see 3 sorts of explanations for such Moon "weakness" :
(1.a) - Historical Moon Ephemeris - just by themselves, i.e. avoiding recourse to some "empirical correction term[s]" - it took an extraordinay long time to produce Moon Ephemeris theories accurate to +/- 6" . Only the Improved Lunar Ephemeris (I.L.E.) by Brown-Eckert (circa 1950) could achieve that goal. And of course all subsequent "theories" whether analytical or numerical integrations have achieved it, and actually can do very much better.
(1.b) - Related subject : what is the accuracy of Modern current CelNav Software incorporating Moon Ephemeris ?
(2.a) - Use of "standard" height corrections tables which are not "fined tuned" to the Moon case, having unavoidable errors reaching 10" in extreme cases due to the use of 2D entries for corrections. Due to the significant Moon parallax, 3D corrections are required because the Earth is not a perfect sphere. Such 3D corrections would be totally unpracticable through tables.
(2.b) - Related subject : are Moon heights corrections adequately 3D performed - i.e. to +/- 3" accuracy - with Modern current Celnav Software ?
(3.a) - Difficulty to adequately "tangent" the Moon Limb onto the visible horizon through sextants ?
(3.b) - Related subject : in critical cases - i.e. in case case of doubt[s] - has the right Moon Limb always been used for the observations ?
Quite strange then that the Moon keeps having such "unreliable" reputation ...
Any explanation ? Any comment ? Anybody ?
Best Regards to all
Antoine M. "Kermit" Couëtte
antoine.m.couette[at]club-internet.fr
