The Sumner line of position furnished ready to lay down upon the chart by means of tables of simultaneous hour angle and azimuth of celestial bodies.

Description

United States Navy Hydrographic Office Publication Number 204. --Followed H.O. Pub. No. 203. Each covered latitudes to 60º. H.O. 203 covered declinations to 27º; H.O. 204 covered declinations from 28º to 63º. In the 1925 editions the title had the phrase ".....AND AZIMUTH OF THE NAVIGATOR'S STARS BETWEEN....." instead. For whole degrees of latitude, with inputs of (whole degrees of) "TRUE ALTITUDE" AND "DECLINATION", hour angle and azimuth are tabulated. Hour angle is given in hours, minutes, and seconds! (Consistent with the American Nautical Almanac then). --Azimuth in degrees to within a tenth of a degree. The tables are designed to solve for the longitude and orientation of the Sumner line that would result if the angular height were in whole degrees. The navigator measures the real height; the (arcminutes of) difference between computed and measured angular heights tells how far (toward or away from the celestial body in nautical miles) his real position line is from the computed one. Solving for longitude had earlier been such an intense focus that it left an emphasis on techniques which solved for the polar angle. This is among the earliest of the modern tabular-method books, but in solving for the polar angle it still has one foot back in the earlier Century. (Later books of tables would assume the polar angle as an input, and solve for the angular altitude of the body).

Subjects

Genres

• Tables

Series Statement

• Publication
• no. 204