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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Were there secret techniques in the 17th and 18th Century
From: Paul Hirose
Date: 2018 Oct 18, 11:41 -0700
From: Paul Hirose
Date: 2018 Oct 18, 11:41 -0700
During WW2 some Japanese sight reduction publications were secret. Bowditch (1984) says, "Japanese H.O. Pub. No. 351, Celestial Navigation Observation Table, was published in 1940-42, in seven volumes for latitudes 0°-70°. The original printing was classified 'secret.' The tables are similar to British Air Pub. 1618, with several differences... Altitudes, including refraction at 4000 meters, are tabulated to a minimum value of 2°." "Japanese H.O. Pub. No. 603, Simplified Celestial Observation Table, was published in 1943. This publication is virtually the same as Pub. No. 351, except that eight additional stars are given, all farther south than those of Pub. No. 351." "Altitude and Azimuth Almanac was published by the Japanese Hydrographic Office, beginning in 1944. Originally, this was a secret publication. Several different versions were printed, and there were some modifications after the first editions. In each, however, the functions of almanac and sight reduction tables were combined. For each of several specific locations, the altitude and azimuth of one or more celestial bodies are tabulated for the date and time, usually at ten-minute intervals. In the earlier editions, the locations selected were important points in the western Pacific. From this practice, these publications are sometimes called 'destination tables.' Later editions used positions differing in latitude by 5°. These tables provided a quick solution for observations made at the tabulated times. On a worldwide basis such a system would involve a very voluminous tabulation each year, or cumbersome corrections."
