Rudimentary Astronomy

61 Cygni aberration accuracy aphelion apogee appear apse axis body calculated catalogue centre comet correction curve describe determined diameter direction discovery disk 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 Hence Herschel horizon inclination increase inequalities instrument interval Jupiter Kepler's known latitude light line of apsides longitude lunar orbit magnitude mass mean anomaly mean distance measured meridian moon moon's moving mural circle nearly node nutation object observations Observatory Otto Struve parallax perigee perihelion period planet planetary polar distance pole position precession proper motions quantity radius vector reader refraction remarkable revolution right angles right ascensions rotation round the sun Royal Astronomical Society satellites Saturn sidereal sidereal period solar orbit space stars sun's supposed syzygy telescope tion transit true anomaly velocity Venus zenith distances