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HO 211 is more complicated and there's greater chance of a blunder,
compared to "inspection tables" such as HO 229 or 249. In the latter,
altitude and azimuth angle are already computed. You only have to look
them up. Of course the tradeoff is a much larger table.

An advantage of HO 211 is that it's not necessary to use an assumed
position (different for each body) in order to get integer latitudes and
LHAs. You simply use your DR position. This partly compensates for the
more laborious computation, and makes for a neater plot.

A disadvantage is that the HO 211 loses accuracy when LHA is near 90 or
270. In fact, exactly at those angles the solution is indeterminate.

Several HO 211 "improvements" have been published. The length of the
table can be cut in half by giving the A and B values for every whole
minute instead of half minute. And by taking advantage of mathematical
symmetry (e.g., A of 10° = B of 80°), it can be halved again.

I've found the latter trick not worthwhile. It's harder to avoid
mistakes, since the A function of an angle is not always in the left
column, and the B values are not distinguished with boldface type. The
redundancy in the original Ageton format doubles the page count, but
twice a small number is still a small number.

HO 211 is small enough that it's sometimes included in other works. My
Bowditch Volume 2 (1981?) has it. So does the 1939 edition of "Practical
Air Navigation" by the U.S. Coast & Geodetic Survey. A scan of that book
is available from the successor agency (NOAA), under the alternate title
"Special Publication No. 197". It's an interesting time capsule of air
navigation techniques on the eve of WW2.

http://www.lib.noaa.gov/collections/imgdocmaps/cgs_specpub.html

   

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