Welcome to the NavList Message Boards.

NavList:

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

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: AN5954 bubble octant by Bausch and Lomb
    From: Gary LaPook
    Date: 2012 May 5, 00:33 -0700
    See if the attached is of help.
    gl

    --- On Fri, 5/4/12, Alexandre E Eremenko <eremenko---.edu> wrote:

    From: Alexandre E Eremenko <eremenko---.edu>
    Subject: [NavList] Re: AN5954 bubble octant by Bausch and Lomb
    To: NavList@fer3.com
    Date: Friday, May 4, 2012, 3:39 PM

    Gary,
    No, unfortunately this is a different (earlier) sextant by Bausch
    and Lomb, which uses an averager.

    In general, the marking of these US Navy octants is
    extremally confusing.
    For example AN5851-1 is also Mark V, but is has
    the varieties 3014-1-A, 3014-1B, 3014-1-C, 3014-2-A, 3014-2-B, 3014-2-C,
    3014-1-D and 3018-1-A, and all these are different:-)

    Is this to confuse the enemy intelligence?
    :-)

    Alex.

    On Fri, 4 May 2012, Gary LaPook wrote:

    >
    > See if this helps.
    >
    > http://fer3.com/arc/imgx/A-6-Octant-Manual.pdf
    >
    > "Don't let the perfect be the enemy of the good."
    >
    > For use in flight, the median is "good enough" (especially considering the magnitude of the other possible inaccuracies)  and a whole lot easier to derive than the average for a changing altitude. Many octants used this method, A-7, A-10, A-12 and your B&L  and probably others.
    >
    > gl
    >
    > --- On Fri, 5/4/12, Alexandre E Eremenko <eremenko---purdue.edu> wrote:
    >
    > From: Alexandre E Eremenko <eremenko---purdue.edu>
    > Subject: [NavList] AN5954 bubble octant by Bausch and Lomb
    > To: NavList@fer3.com
    > Date: Friday, May 4, 2012, 1:53 PM
    >
    >
    > Dear List members,
    >
    > Does anyone have this octant or a manual to it?
    > I see a picture and a description in Ifland's book.
    > Unfortunately this description makes no sense for me:-(
    >
    > The main distinction from all other air octants is that
    > it is "medianizing" instead of averaging.
    > Instead of averaging it takes a median of 15 altitudes,
    > with a very simple "medianiser". There is a picture which
    > is supposed to show this medianiser in action, and it seems
    > clear how it works.
    >
    > Let me recall what is the median. You order 15 numbers by their
    > magnitude and take the 7-th. This is the median.
    > Median has some substantial advantages in comparison with
    > the average, if you repeatedly measure the SAME quantity.
    >
    > This does not apply however to sextant altitude observatons,
    > except for the Polaris and Sun at Noon.
    > In general, altitude changes quite quickly and when you take 15 shots,
    > the results are very likely to be increasing or desreasing.
    > In which case there is evidently no point of taking the median.
    > (It will be simply the 7-th shot).
    >
    > That's why I am looking for a more reasonable explanation of how this
    > sextant really works, or what is it for.
    >
    > Alex.
    >
    >
    >
    >
    >
    >
    >
    >
    > View and reply to this message: http://fer3.com/arc/m2.aspx?i=119377
    >
    >
    >

    File:

      
       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    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:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    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