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    05-10+11 Lunars + scope adjustment
    From: Fred Hebard
    Date: 2003 May 9, 15:26 -0400

    Doug,
    
    Regarding the alignment telescope.  This procedure is described also in
    Bowditch, without the wires.  Again, Bowditch says to chose two stars
    at least 90 degrees apart and to note the angle, but no further mention
    is made regarding use of that angle.  I presume then that one notes the
    angle to be sure it is at least 90 degrees.  Perhaps others have more
    knowledge of this?
    
    One would bring the stars into confluence at one wire, and then check
    that they are still in confluence at the other wire.  Without the
    wires, Bowditch says to bring two stars into confluence at one side of
    the scope and then move them to the other side to check that they
    retain confluence.  Whether they separate or overlap would then tell
    one in which direction to adjust a scope that was out of alignment.  I
    don't think modern sextants have provision for making this adjustment
    in the field.
    
    The wires may originally have had another use.  Similar wires used to
    be located in land-based astronomical telescope eyepieces.  One would
    note the time when celestial objects crossed each wire, to better
    compute ephemerides and such.  This may also have been the original
    purpose of the sextant wires, for land-based observations using an
    artificial horizon.  Perhaps others can enlighten us as to the purpose
    of the wires.
    
    Simex or Takizawa, sextants have alignment scopes with two wires.
    
    Fred
    
    
    

       
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