套件：astronomical-almanac（5.6-7）

astronomical almanac - calculate planet and star positions

The aa program computes the orbital positions of planetary bodies and performs rigorous coordinate reductions to apparent geocentric and topocentric place (local altitude and azimuth). It also reduces star catalogue positions given in either the FK4 or FK5 system. Data for the 57 navigational stars is included. Most of the algorithms employed are from The Astronomical Almanac (AA) published by the U.S. Government Printing Office.

The aa program follows the rigorous algorithms for reduction of celestial coordinates exactly as laid out in current editions of the Astronomical Almanac. The reduction to apparent geocentric place has been checked by a special version of the program (aa200) that takes planetary positions directly from the Jet Propulsion Laboratory DE200 numerical integration of the solar system. The results agree exactly with the Astronomical Almanac tables from 1987 onward (earlier Almanacs used slightly different reduction methods).

Certain computations, such as the correction for nutation, are not given explicitly in the AA but are referenced there. In these cases the program performs the full computations that are used to construct the Almanac tables (references are provided).

標籤: 領域: 天文學, 角色: 程式, Purpose: 學習

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