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    Navy Mark V Sextant, Accuracy
    From: Peter Henry
    Date: 2004 Dec 23, 23:34 -0500

    I would like to receive some advice on two questions regarding the standard
    accuracy with this sextant.  I have been using the instrument occasionally
    for approximately 1 year and learned to use a sextant from books.  I have
    done calculations by hand but also with the computer program mac nav.
    I find that I get wildly varying accuracy from the most accurate of 1.5nm to
    30nm approximately.  I will also take multiple sites and have a varying
    range of 15 nm between the sites.
    I understand that the way to use this instrument is to center the bubble on
    the cross in the field of view and then to bring the object down to a point
    parallel to the horizontal line of the cross on either side of the bubble.
    Occasionally with stars I can bring it down centered in the bubble due to
    there small size.  I also understand that the bubble should be twice as big
    as the object.  Is this the right way to use this sextant?
    Secondly can a magnifying scope be added to this sextant to increase ones
    ability to precisely place the object on the horizon?
    What is the standard level of accuracy for this sextant?
    I also find that I must refill the bubble level every few months, that
    initially after filling the bubble I can change it's size up and down, but a
    few months out I can no longer reduce the bubble size.  Obviously the bubble
    or one of the storage reservoir is leaking but I see no fluid though the
    sextant has a distinct smell which I assume is the fluid being turned into a
    gas.  How do I find and fix this leak?
    Peter Henry

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