Rudimentary Astronomy

61 Cygni aberration accuracy angular distance aphelion apogee appear axis body calculated catalogue centre comet describe determined diameter direction discovery disk diurnal motion earth earth's orbit earth's surface ecliptic effect elements elliptic orbit epoch equal equator equatorial equinox error evection excentricity fixed geocentric gravitation Greenwich heavens heliometer Hence Herschel horizontal Huggins inclination inequalities instrument Jupiter Kepler's known latitude light line of apsides longitude lunar orbit magnitude Mars mass mean anomaly mean distance measured meridian moon moon's nearly nebulæ node nutation object observations Observatory Otto Struve parallax perigee perihelion period planet planetary polar distance pole position precession proper motions quantity reader refraction remarkable revolution revolve right angles right ascension rotation round the sun Royal Astronomical Society satellites Saturn sidereal sidereal period space spectrum stars sun's superior planets supposed syzygy telescope tion transit true anomaly velocity Venus visible zenith distances