Outlines of Astronomy

altitude amount angle angular appear apsides ascertained astronomers axis bright calculation celestial centre circle comet curve described diameter difference direction disc distance disturbed body disturbing force diurnal diurnal motion double stars earth ecliptic effect elements ellipse epoch equal equator equinoctial equinox error exact excentricity fixed globe gravity heavens heliocentric horizon inclination increase inequality instance instrument interval Jupiter latitude latter less light longitude lunar magnitude mass mean measure meridian moon moon's motion nearly nebula node normal force nutation object observed orbit parallax parallel perigee perihelion period perpendicular perturbations planet planetary pole portion position precession proper motions proportion recede recess reckoned refraction remarkable render respect result revolution right ascension rotation round satellites Saturn seen sidereal sidereal day sidereal period situation solar sphere spherical stars station sun's suppose syzygies tangential force telescope tion Uranus variation velocity visible whole zenith