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    Re: bubbble sextant info...
    From: JC Sutherland
    Date: 2000 Mar 28, 4:21 PM

    Russell Sher wrote:
    > See this site for info. including a downloadable scanned user manual for a
    > bubble sextant:
    > http://www.physics.uq.oz.au/physics_museum/bblsex.html
    > regards
    > Russell
    To Russel et al;
    I have two Bubble sextants and  I have had them for many years. One of these I
    have modified to use it as a Marine sextant and found it very useful. I paid a
    piffling price for it in the days when Government Surplus shops were on every
    street corner, (well nearly).
    The standard Mk 9a and b  sextants were used during the war for aircraft
    navigation and  are now getting quite rare.
    They were never much use at sea as the bubble could not be kept still even in
    the quietest conditions and the direct view of the horizon was not possible
    without considerable modification to the instrument - but it could be done.
    However they were excellent instruments for practice on land and a student of
    mine once used one for navigating in the Australian outback!
    The crux of using these instruments is getting and controlling the bubble, If
    there is still liquid present in the bubble chamber then it may still be worth
    restoring it but many have now dried up and some of those that havn't have
    corrosion on the inside of the bubble chamber window and this makes the bubble
    stick, destroying the accuracy.
    A servicable sextant could be read to 1 min of arc and would be accurate to
    about 0.5' with the clockwork mechanism working.
    I also  have the manuals for these sextants if there is any interest.

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