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    Re: Corrections for use of artificial horizon at 1,000' MSL?
    From: Alexandre Eremenko
    Date: 2012 Mar 13, 11:27 -0400

    Dear Scott,
    When observing with the  artificial horizon, you
    1. Correct for the index error.
    2. Divide the result by 2.
    3. Correct the result for refraction for the altitude
    obtained on step 2. (Yellow page in the Almanac).
    4. Use table on p. A4 of the Almanac to correct for the
    temperature and barometric pressure at your altitude.
    For this you can use a barometer, or use the weather broadcast
    from the nearby airport, taking the difference of your altitude
    from the airport into account, if it is substantial.
    
    You enter all tables with the altitude obtained on Step 2.
    
    The result is your observed and corrected altitude.
    
    Your altitude of 960 feet over the sea level probably does not matter much
    for refraction, and most of the correction for it, will come from table
    A4. Only in high mountains you will probably need an additional
    correction.
    
    Myself, I use A4 correction only in winter, or when doing lunars,
    using a home barometer, or my airport pressure.
    
    
    Alex.
    
    On Tue, 12 Mar 2012, Scott Statz wrote:
    
    >
    > I live in Madison, WI, at about 960' mean sea level.
    I am teaching myself with the help of CELESTIAL NAVIGATION BY H.O.249
    by John E. Milligan and am still working my way through the book.
    When using an artificial horizon, do I need to be concerned with
    a special correction for refraction
    (anything else at this altitude or in my circumstance)?
    I understand its not necessary at sea level and there are concerns when taking a sight at low angles.
    >
    > Thanks
    >
    > Scott
    >
    >
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