Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Bubble sextant instructions
    From: Capn MCL Rodaway
    Date: 2001 Dec 14, 7:43 PM

    Thanks for the info Clive & everyone else.  I have no plans for taking it
    with me out to sea, more for fun at the end of the pier.  They're just not
    as comfortable to handle as a proper sextant.
    Yours Aye
    Michael Rodaway
    Seamen, with their inherent sense of order, service, and discipline, should
    really be running the world.
    on 12/12/01 19:04, J.Sutherland at jcs{at}CWCOM.NET wrote:
    > Cap'n Rodaway;
    > I have used the Mk9 sextant for many years. In its
    > unmodified form it is of
    > little use at sea as it is generally impossible to
    > keep the bubble steady
    > enough, although I confess I have never tried it
    > from the deck of a large ship.
    > If the steadyness of the vertical is tolerable,
    > then the vibration of the deck
    > caused by the engines can be an advantage.
    > These sextants are very old now and deterioration
    > of the glass surface on the
    > inside of the bubble chamber tends to make the
    > bubble stick (especially if it
    > is small) and the vibration helps in unsticking
    > it. Adjusting the bubble size
    > is a knack but it is surprising how many of these
    > sextants have retained their
    > liquid filling
    > War surplus sextants were frequently modified by
    > removing the bubble chamber
    > and adding a prism to arrange a simultaneous view
    > of the horizon. I have
    > modified (one of the earlier ones that didnt have
    > the averaging clock)  by
    > drilling a hole through the front and replacing
    > the 'horizon mirror' with a
    > split mirror (to produce the familiar arrangment),
    > while retaining the bubble
    > for use on land. The biggest problem with this
    > arrangement is that the glare
    > filters are in the combined light path and only a
    > strong horizon combined with
    > a weak Sun gives ideal sights.
    > The sextant Mk IX with the clockwork averaging is
    > ideal for back yard
    > navigation and accuraces of less than + or - 1
    > minute can be achieved with
    > practice. Without mechanical averaging it will be
    > necessary to take up to a
    > dozen sights and average the result by graphing
    > the data.
    > The small bulbs for illuminating  the bubble and
    > the scales are very difficult
    > to find and even seriously damaged sextants should
    > be aquired if only to
    > caniballise  these bulbs.
    > Without them only Sun sights are possible
    > The web site below is what you are looking forif
    > it is still running. The
    > reproduction is poor quality but if you have any
    > trouble come back to me and I
    > will photo copy my booklet for you.
    > Have fun!
    > Clive Sutherland
    > Abingdon UK
    >> http://www.physics.uq.oz.au/physics_museum/bblsex.html
    > Cap'n MCL Rodaway wrote:
    >> I was wondering if any one can point me to a web site or any other source
    >> for a instructions on using a WWII RAF Bubble Sextant Mark IX A.  Also what
    >> differences, if any, are there in working the sight with it, compared to a
    >> marine sextant?
    >> Yours Aye
    >> Michael Rodaway, M.N.

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site