Sight Reduction Tables Pub. 229

Without a calculator or computer programmed for sight reduction, the navigator needs sight reduction tables to solve the celestial triangle. Two different sets of tables are commonly used at sea.

NIMA Pub. 229, Sight Reduction Tables for Marine Navigation, consists of six volumes of tables designed for use with the Nautical Almanac for solution of the celestial triangle by the Marcq Saint Hilaire or intercept method. The tabular data are the solutions of the navigational triangle of which two sides and the included angle are known and it is necessary to find the third side and adjacent angle.

Each volume of Pub. 229 includes two 8 degree zones, comprising 15 degree bands from 0 to 90 degrees, with a 1 degree overlap between volumes. Pub. 229 is a joint publication produced by the National Imagery and Mapping Agency, the U.S. Naval Observatory, and the Royal Greenwich Observatory.