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: Navy MK 5 Octant Using Natural Horizon
    From: Greg Rudzinski
    Date: 2012 Apr 30, 21:13 -0700


    "T" is Toward
    "A" is Away

    The spread or scatter difference between the two sets of 30 observations is 0.6' (2.7' - 2.1') therefor +/- 0.3' will be the improved benefit of the preset on expected max error for any individual observation.

    You will have to examine a U.S. Navy MK 5 bubble octant to get a better idea of what I'm trying to do. The micrometer drum on the MK 5 is only marked in even minutes. The whole point of this exercise is to overcome the inaccuracy caused by having just the even minutes of arc unlike a marine sextant which has the micrometer drum marked every minute plus a scale to determine tenths.

    Yes the observations were made from the beach using the natural horizon. There is no way to get results like I did with a bubble horizon even on my luckiest day ;-)

    Yes you are correct in that there is no difference but only when averaging multiple observations. I,m interested in the possible error for a single observation.

    I was happy to get near marine sextant performance which means that this particular octant with horizon prism is good enough to substitute for a marine sextant aboard ship or small craft.

    Greg Rudzinski

    [NavList] Re: Navy MK 5 Octant Using Natural Horizon
    From: Alexandre Eremenko
    Date: 30 Apr 2012 19:57
    There is something I don't understand in your messag:

    > Preset micrometer- Intercept average 0.2' T with spread
    > (scatter) of 2.1' moa.

    What does the letter "T" mean after the 0.2' ?

    > Normal set micrometer- Intercept average 0.1' A with spread of 2.7' moa.

    What does the letter "A" mean after the 0.1'
    "Intercept average" means the "average error", correct?

    > Conclusions:
    > A small improvement (+/- 0.3' moa) for single
    > observations can be realized by presetting the Navy MK 5 micrometer drum
    > to the even minute then waiting for horizon tangency.

    I don't see how your data imply this conclusion:-)
    I would interpret your data as showing that "there is no difference"
    whether you preset or not.

    And the last question: why do you have to preset to even minute?
    Why not to odd?

    The observations were made from land, I supose, and with natural horizon,


    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

    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