The Sight Reduction Tables for Air Navigation consist of three volumes of comprehensive tables of altitude and azimuth designed for the rapid reduction of astronomical sights in the air. The present volume (Volume 1) contains tables for selected stars for all latitudes, calculated for the epoch of 2010.0, and replaces the previous edition calculated for the epoch of 2005.0; it is intended for use for about 5 years, when a new edition based on a later epoch will be issued. Volume 2 for latitudes 0°– 40° and Volume 3 for latitudes 39°– 89° are permanent tables for integral degrees of declination. They provide sights for bodies with declinations within 30° north or south of the equator, which includes the Sun, the Moon, the navigational planets and many of the navigational stars.
The time argument in the examples is denoted by UT (Universal Time). It is also known as GMT (Greenwich Mean Time).
Sight Reduction Tables for Air Navigation are published in the USA as Pub. No. 249, and in the UK as Rapid Sight Reduction Tables for Navigation AP 3270/NP 303. The National Geospatial-Intelligence Agency (NGA) is responsible for the compilation and composition of these tables. The Nautical Almanac Office of the U.S. Naval Observatory and H.M.
Nautical Almanac Office (HMNAO) of the UK Hydrographic Office have cooperated in their design and preparation. Some of the auxiliary tables in this edition were furnished entirely by HMNAO.
The content and format of these three volumes may not be changed without the approval of Working Party 70 of the Air Standardization Coordinating Committee.
Description of the tables
These tables, designated as Volume 1 of the three-volume series of Pub. No. 249, Sight Reduction Tables for Air Navigation, contain values of the altitude (to the nearest minute) and the true azimuth (to the nearest degree) of seven selected stars for the complete ranges of latitude and hour angle of Aries. The arrangement provides, for any position and time, the best selection of seven of the stars available for observation and, for these seven stars, data for presetting before observation and for accurate reduction of the sights after observation.
In the calculation of the altitudes and azimuths the mean places of the stars for epoch 2010.0 have been used; corrections for precession and nutation are given in Table 5, but their omission will not give rise to a positional error greater than two miles in the years 2007–2012. No correction for refraction has been included in the tabulated altitudes, so that the full correction must be applied to the sextant altitudes.
Although Pub. No. 249 was designed for air navigation, it is also used extensively for marine navigation. The main differences in the use of Pub. No. 249 for marine navigation are highlighted at the end of this introduction. Volume 1 may be used without reference to an almanac such as The Air Almanac or The Nautical Almanac. The tables in this volume may be used with a clock, or other device, giving sidereal time. With the normal procedure of plotting a sight from an assumed position, no interpolation is required for the stars tabulated.