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    Re: Moon - Antares
    From: NavList
    Date: 2009 Jan 22, 12:23 -0800

    You bring up a special case in navigation, the lunar occlusion of a bright 
    star or planet.  I cannot determine from your lat lon, if the moon covered 
    Antares or not.  It may have.
    
    The occlusion events offer the special case of the Lunar Distance equal to 
    zero. An occlusion event of bright stars and planets is offered in the 
    Astronomical Almanac and online at the United States Naval Observatory.  
    There are two features of the event, one when the bright star or planet 
    disappears (immersion) and another when it re-appears (emmersion).
    
    In either feature, there is no sextant needed, only the time of the event, 
    since bright stars have no perceptible diameter and bright planets have tiny 
    perceptible diameters.
    
    I have experimented with Mr. Reed's online lunars tool and have found that I 
    can obtain what appears to be the correct result for the immersion of Antares 
    for my lat, lon vs that which is illustrated online at the USNO for the June 
    event.  I cannot get the tool to function for the emmersion of the same 
    event.  I suspect that Mr. Reed's program does not function for the 
    non-illuminated limb.  That would be an odd lunar, an un-illuminated limb is 
    not used.  
    
    Bowditch's navigator, mid 1800's, offers a method of solving this event and in 
    particular offers it up as a method of correcting your chronometer. 
    If your chronometer was accurate, however, it could be flipped over to determine longitude.
    
    Best Regards
    Brad
    
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    [Sent from archive by: bmorris-AT-tactronics.com]
    
    
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