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Peter Hakel, you wrote:
"The Volume 1 of HO 249 tables intended for air navigation includes "Table 1: 
Altitude correction for change of position of observer" and "Table 9: 
Coriolis (Z) correction" table.  This just occurred to me and I haven't 
thought about this in detail yet.  Could these tables be of any use for the 
noon curve construction on a vessel moving during the half-hour or so before 
and after LAN?  I realize that ships do not move as fast as aircraft, but it 
looks like our aviator friends have already considered and solved this 
problem, so perhaps we can learn from them.  The only difference should be in 
the magnitude of the ground speed, which should make the corrections even 
easier on more slowly moving surface ships."

The Coriolis correction is required because the sextant is accelerating in the 
aircraft. This causes the bubble to indicate something different from the 
true vertical. This correction is best categorized as a "sextant correction" 
like index correction. It is a property of the instrument and its behavior 
when moving.

The correction of the noon curve for motion is nothing more than the 
correction for a running fix. Imagine solving a noon curve set of sights by 
plotting LOPs. You would have to advance the earlier sights to "catch up" to 
the later ones. Since all of the LOPs are nearly parallel (the Sun's azimuth 
changes by a relatively small angle), this advancing is equivalent to 
changing the observed altitudes by an amount proportional to speed and 
elapsed time. Try it on paper if you need to convince yourself. 

-FER




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