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    Ageton HO 211 accuracy 1944 article
    From: Paul Hirose
    Date: 2015 Oct 29, 13:16 -0700

    I have the Ageton sight reduction table in three different books but
    don't own a bona fide HO 211. Due to recent discussion I thought maybe
    it's time to buy one. While searching the Web I came across a 1944
    article at the ADS site on HO 211 accuracy by Samuel Herrick. He notes
    Ageton's claim of .5 minute accuracy without interpolation and his
    caution about hour angles near 90 degrees. So is it safe to infer his
    accuracy claim is valid whenever the caution is not applicable?
    
    No, says Herrick. In fact, the maximum error can reach about 6 minutes
    without interpolation. A major source of error is the step where you
    look up function A of side R and take out B of R. (R is the side that is
    perpendicular to the meridian and common to both triangles.)
    
    "The interpolation of B(R) from A(R) will alone reduce the maximum error
    to about two miles for K = 90°, 0.8 mile for K = 80°, and thus bring the
    error within practical limits for most navigation problems."
    
    "In fine, the maximum error of 30 miles that may be found in the use of
    Ageton's table without interpolation sets a dangerous trap for the
    unwary navigator, especially if he be an airman making a sun-line
    approach at sea. But forewarned, he will find a way to his taste for
    avoiding it."
    
    Samuel Herrick, THE ACCURACY OF AGETON'S METHOD IN CELESTIAL NAVIGATION,
    Publications of the Astronomical Society of the Pacific, Vol. 56, No.
    331, p.149 (August 1944).
    
    http://adsabs.harvard.edu/abs/1944PASP...56..149H
    

       
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