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: Navy MK 5 Octant Using Natural Horizon
    From: Greg Rudzinski
    Date: 2012 May 1, 15:36 -0700

    Alex,

    The index error doesn't have to be odd, even, or a whole number. For bubble aircraft octants there is no need to try for fractions of a minute and since the micrometer drum is scaled in even minutes the index error is best determined to the nearest whole minute. On my octant the true index error is probably somewhere between 5' and 6' moa but 6' moa looks to be the closer whole moa. This 6' moa can be adjusted out but is a difficult bit of business unlike a marine sextant.

    Greg Rudzinski


    MK 5 Octant Using Natural Horizon
    From: Alexandre Eremenko
    Date: 1 May 2012 17:37
    Greg,

    > Spread or scatter has been used here on the list to describe
    > the difference between maximum and minimum values. Not sure what the
    > statistics term is (variance ?).

    I don't think there is a standard term, but "spread" is Ok.
    Variance is different: it is usually defined as
    the square root of the average of the squares of individual deviations.

    > On preset observations the micrometer is set exactly on an
    > even minute of arc then the time is mark when the Sun's lower limb
    > touches the horizon (fingers are off the micrometer).

    This is the usual method recommended with ordinary sextant (when observing
    the Sun). At least Russian manuals recommend it for the Sun.

    One thing which surprises me is that your Index Correction happens
    to be so nearly close to 6' (even minutes!).
    Suppose it were 5' in reality.
    Then you would determine it either as 4' or as 6',
    and your whole series would have a systemanic bias of 1'.

    The difficulty of determining the Index Error with high precision was
    many times discussed on this list.

    Also I suppose that your scope has power 1.5x or something like this.
    Anyway, there are many reasons I could imagine which would lead to
    errors much larger than you have.

    Alex.

    ----------------------------------------------------------------
    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com
    ----------------------------------------------------------------

       
    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