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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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