Abstract
Calculation formulae of E (or GHA) and d of celestial bodies suitable for small computers on board were investigated. The following expressions were found to be the simplest: For the sun: Combination of a polynomial and Fourier series, For planets: Fourier series, without synodic periods, For stars: Approximation of the Bessel-Suzuki formula ; merely the principal term (moon's node, 18.6 yrs.) is adopted for nutation, and the earth's orbital velocity is substituted by the sun's mean anomaly to calculate aberration. Mean errors of the empirical formulae for the sun and planets are within ±0^s.3 in E and ±0'.04 in d. By the approximation formulae for stars, errors are within ±0^s.1 in E (except for Polaris) and ±0'.01 in d
