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    Re: Navy MK 5 Octant Using Natural Horizon
    From: Greg Rudzinski
    Date: 2012 May 1, 14:54 -0700

    Alex,

    The results are not extraordinary in that any data set from any sextant can be made to look good by adjusting the index error. This is why I look at the maximum and minimum values of a set of data to judge a sextant and or navigator performance. To illustrate what I'm talking about I will do a set of 30 observations with a Tamaya Jupiter equipped with a 7 power scope. The overall average will be something less than 1 moa but what will show best is the narrow range between the maximum and minimum values. For the Navy MK 5 octant the maximum and minimum differed by 2.4' moa if all 60 observations are taken into account. For a 7 power scope attached to a marine sextant the maximum and minimum values should be less than 1.5' moa. We shall see in a few days if the fog ever lifts here.

    The 0.2' moa number is the average intercept of the 30 preset observations.

    The octant scope is 2 power.

    Keep an eye open on ebay for U.S. Navy MK 5's which can be had for under $100 but use caution on the buy. If for some chance the bubble chamber is not working on these octants they are still good as a conventional sextant but it is nice when the whole package works-bubble, averager, lighting system, horizon prism, and astigmatizer .

    Greg Rudzinski

    [NavList] Re: Navy MK 5 Octant Using Natural Horizon
    From: Alexandre Eremenko
    Date: 1 May 2012 17:27
    Dear Greg,
    Thanks for the data. I reduced the results and obtained the same errors.
    One more question: you preset the octant.
    Why did you preset on such random altitudes without any apparent pattern?
    How did you decide on which altitude to preset?

    I repeat that the results look extraordinary to me.
    I mean I have never seen anything like that.

    > By presetting I am on an exact moa of the micrometer drum so
    > the measurement precision will be about 0.2' moa.

    Where does this number 0.2' come from? From the average of
    your whole series?

    I regrett that my bubble octant does not have this feature
    of observing with the real horizon:-)

    What is the telescope power btw?

    Alex.

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