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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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