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
    An5851 bubble sextant manual and use questions
    From: Michael Dorl
    Date: 2003 Jan 4, 14:48 -0600

    I recently acquired a an5851 bubble sextant.  As far as I can tell, it is
    fully functional but being un tutored in its use, I am having some
    difficulties so permit a few questions from the uninitiated....
    1) I found a manual (dated 20 March 1945) on the web with pages i to v and
    1 -16.  This seems like the front of a bigger manual since these pages
    offer little more than a description and the introduction promises 'This
    manual contains instructions for the Installation, Operation, Maintenance,
    and Overhaul..."
    1a) Are these pages really all that exist or is this just the front of a
    bigger manual?
    1b) Is there any source for the complete manual?
    2) Let me describe what I see when I form a bubble and look through the
    instrument.  The bubble looks like a black well defined dot with a clear
    transparent spot within it.  I can remove the bubble completely and form a
    new one of varying sizes.  Small bubbles (say smaller than six Sun
    diameters or two minutes) are sluggish and don't respond well to movements
    of the sextant.  The clear spot is not exactly centered and moves about
    within the black dot.
    I have been using the clear spot as a peep sight and centering the target
    within it.  On one occasion with a large bubble I did observe a reduced
    sized image of the target (sun) in the center of the dot (which did not
    coincide with the clear spot).  I have also seen the whole dot to be
    illuminated when the sun was in its center.
    2a) So how big a bubble should be used?  How many sun diameters?
    2b) What is the recommended observational method?
    use clear spot as peep sight?
    guess where center of dot is and align with target?
    2c) is the bubble acting as a lens collecting light and concentrating it
    within the clear spot?
    Any insights you can provide or pointers to existing information on these
    questions would be greatly appreciated.
    Mike Dorl
    Madison WI

    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