NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Antoine Couëtte
Date: 2022 Aug 8, 12:10 -0700
Good day to you Frank,
If no error or typo on my behalf,
from N47°00.0' / E 009°50.0' i.e. starting from an already known position, and therefore only - in some way - using part of the available data since I am no longer using here the heights which helped me earlier to determine such position :
03:35:00 MOON LL Hs = 40°06.76' / Az = 92.97° Procyon Hs = 09°56.00' / Az = 92.98° Topocentric LD as read in Sextant = 30°10.76'
03:45:00 MOON LL Hs = 41°46.47' / Az = 94.84° Procyon Hs = 11°37.58' / Az = 94.87° Topocentric LD as read in Sextant = 30°08.89'
Rate of change as observed in the Sextant : -1.87' over a 10 minute period which is 600 seconds of time.
Hence a 0.1' rate of change observed in the Sextant is equivalent to 600 seconds of time x (0.1 / 1.87) = 60 / 1.87 = 32.1 seconds of elapsed time.
I am measuring topocentric angles with an instrument. Therefore I am applying a proportional rule to the very data I am measuring - topocentric angles vs. times - as pertaining / applicable to the tools I have in my hands.
Again, this result is applicable for a previously known position without using the heights any more.
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If I were not starting from a previously known position - which should rather be the case here - I cannot draw valid conclusions from only the LD's since I am also measuring and using other data (namely the heights).
Hence it is perfectly OK with me that the heights measurements may significantly improve / compensate for the uncertainty on UT indicated here-above for a fixed position known in advance.
BTW and again, and before I skip it, what are your own numbers as regards actual UT determination ? And through which method did you derive them ?
Kermit
