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    Coriolis vs Noon curve correction
    From: Frank Reed
    Date: 2009 Apr 25, 20:46 -0700

    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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