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    Re: Index Error - Real vs. Artificial Horizon
    From: Greg Rudzinski
    Date: 2013 Feb 28, 13:42 -0800

    Paul,

    What you have just discovered is sextant parallax. The horizon should be no less than 2 miles distance which means your height of eye needs to be over 4 feet. Using the filtered Sun is another way to check index error. Be sure to filter the horizon mirror as well as the index mirror. Lots in the archives on this.

    Greg Rudzinski


    [NavList] Index Error - Real vs. Artificial Horizon
    From: Paul Fithian
    Date: 28 Feb 2013 13:24
    While playing around with the sextant, I've noticed a big difference in index error when viewing things far away vs. near.

    For example, if I adjust the horizon mirror so that a near (5' away) horizontal line matches up through the glass and the mirror images, these images don't line up when I view a horizontal line that is several hundred feet away.

    Which one do I choose to apply the right index correction for the artificial horizon readings? I know I have to take the Hs, apply index correction, then take 1/2 of this reading to get Ho.

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