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    Re: Lunars calculator
    From: Frank Reed
    Date: 2005 Apr 8, 18:15 EDT

    Bill, you wrote:
    "A line perpendicular to a line through the horns  points at the Sun?  Had not
    thought about using that to align the  sextant. Thanks."
    
    Yes, it's very useful. This instruction was included in  Maskelyne's
    instructions on lunars in the earliest Nautical Almanacs. You can  read his
    instructions and maybe get a feel for the early attitudes in the online  scan of the
    1805 N.A. on the Blunt-White Library web pages at Mystic Seaport's  web site:
    www.mysticseaport.org
    
    And you wrote:
    "Moon was approx. 53d,  and dim against the sky.  Given the Sun was lower, it
    might have made  sense to us it in the horizon glass instead of the Moon, but
    it seemed easier  to have the Moon in the glass as it was difficult to see."
    
    This is  probably another reason why navigators in the 19th century seem to
    have avoided  lunars when the Moon's elongation was less than about 50 to 60
    degrees. The  contrast against the sky is just too darn low. Of course, they
    could have waited  until dark and used stars if really necessary.
    
    By the way, that mystery angle you were wondering about... it's the
    difference in azimuth between the two bodies.
    
    -FER
    42.0N 87.7W, or  41.4N 72.1W.
    www.HistoricalAtlas.com/lunars
    
    
    

       
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