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    Index correction
    From: Alexandre Eremenko
    Date: 2013 Jan 23, 16:47 -0500

    As I reported to the list earlier, my observation
    of the small Lunar distance when the Moon was close to Jupiter
    was successfull, except the unexpected large change in the Index error.
    At noon before the observation I checked it with Sun, it was -0'4,
    and the check seemed very reliable (small scattering, and 4SD matched).
    
    Then I took the Lunar in extreme cold, the temperature dropped from
    about 40F at noon (in fact I observed at noon from my room,
    so the sextant was under the room temperature) to 8F at the time of Lunar
    observation, (the sextant was brought outside 1/2 before the observation)
    the first measured distance was terrible (almost 2' error with -0'4 IC) so
    I rechecked
    the IC from stars and found -1'2 (also very consistently, 5 or 6 different
    star observations). After that the Lunar was OK, not only the short
    one but also a long one.
    
    Next day I checked again with Sun in the morning. The temperature was
    20F, and I cooled the sextant for 1 hour outside before the observation.
    The index error was -0.5.
    
    If this is really temperature dependent fluctuation, is not it
    too large for a high quality metal sextant ?
    
    Alex.
    
    
    
    
    

       
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