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

    Alex,

    "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
    Greg,
    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,
    correct?

    Alex.

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