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    Re: Bubble Sextant
    From: Hewitt Schlereth
    Date: 2008 Jul 11, 11:38 -0400

    Are there any sources for these sextants?  HewS
    On 7/11/08, engineer  wrote:
    >  The British Mk IX is about 200 grams lighter. and is  my favourite
    >  because all the controls come readily to hand, it is easy to use and
    >  read and you have a reasonable chance of getting one that works. With
    >  the exception of the averager on the Mk IX A, the works of the Mk IX
    >  series are accesible and usually easy to fix. The bubble assembly is
    >  also easy to refill.
    >  My A7 has a vapour pressure bubble chamber which, if empty when you
    >  get it is very difficult for the non-specialist to refill. Many of the
    >  WW II US instruments suffered from "complification" and some used 4
    >  prisms, heavy and expensive to produce. The AN 5854-1's
    >  averager(strictly, a median device)is temperamental and hard to fix if
    >  it has suffered corrosion in storage. The AN 5851(Navy Mk 5)is heavy
    >  and clunky and initial setting of its averager needs care. The A10-A
    >  is perhaps the handiest instrument to use, provided the electrical
    >  marking system is in good order. It is not impossible for
    >  a reasonably handy person to fix the system, once it has been
    >  understood. The A10 uses the Mark I finger to operate the marking
    >  pencil. That leaves rarer instruments, like the A8-A and the Navy Mk
    >  IV. The latter was plainly not a success and if you find one, the
    >  averaging system will tax the average person to fix. The A12 is a
    >  favourite of many people and was designed to be cheap to produce(some
    >  of the others cost almost the price of a small home to produce). The
    >  arc and vernier on mine are poorly cut, but if you can get one free
    >  from corrosion and in working order it would be a good one to start
    >  with.
    >  The Achilles heel of nearly all the bubble sextants is the bubble
    >  chamber. For practical purposes, you cannot refill a vapour pressure
    >  chamber. Happily, most of the later bubble sextant produced used a
    >  different system with an air reservoir; and these are fairly easy to
    >  refill. The MA series are, alas, expensive and do not often come on to
    >  the market.
    >  Bill Morris
    >  On Jul 11, 1:54 pm, "Gary J. LaPook"  wrote:
    >  > My fravorite is my MA-1 which isn't a bubble sextant but a pendulous
    >  > mirror type and my second favorite is the MA-2 with a bubble. If you
    >  > want a light, simple sextant get a Bendix A-7, it is the lightest bubble
    >  > sextant I have.
    >  >
    >  > gl
    >  >
    >  >
    >  >
    > > glap...@pacbell.net wrote:
    >  > >Here is a link to a site with discriptions of many types of bubble
    >  > >sextants:
    >  >
    >  > >http://home.earthlink.net/%7Es543t-24dst/airnav/index.html
    >  >
    >  > >gl
    >  >
    >  > >On Jul 5, 3:19 am, glap...@pacbell.net wrote:
    >  >
    >  > >>You should also check the files section of the Yahoo sextant group for
    >  > >>more information on sextants.
    >  >
    >  > >>http://groups.yahoo.com/group/Sextants/files/
    >  >
    >  > >>gl
    >  >
    >  > >>On Jul 3, 5:14 pm, bubi352  wrote:
    >  >
    >  > >>>I am new to this group and new to celestial navigation. I currently
    >  > >>>work as an airline pilot and fly extensively over water at night. I
    >  > >>>have developed a keen interest in determining my position the old
    >  > >>>fashion way.
    >  >
    >  > >>>Could someone tell me which bubble sextant I should buy?
    >  > >>>What should I be looking on a bubble sextant?
    >  > >>>Where can I buy one?
    >  >
    >  > >>>Thank you in advance.
    >  >
    > > >>>Bubi- Hide quoted text -
    >  >
    >  > - Show quoted text -
    >  >
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