Rudimentary Astronomy

61 Cygni aberration accuracy accurately angular distance aphelion apogee apparent apse astronomers calculated called catalogue comet computed correction curve describe determined diameter difference direction disk diurnal diurnal motion earth earth's centre earth's orbit earth's surface ecliptic effect equal equator equatorial equinox error of collimation evection excentricity fixed geocentric gravitation Greenwich heavenly bodies heavens Hence horizontal inclination increase inequalities instrument Kepler's known latitude line of apsides longitude lunar orbit magnitude mean anomaly mean distance measured meridian micrometer microscopes moon moon's motion moving mural circle nearly node nutation object object-glass observations observatories parallax passes the meridian perigee perihelion planet polar distances pole position precession proper motions proportion quadrature quantity reader refraction revolution revolve right angles right ascension rotation round the sun satellites sidereal space stars sun's supposed syzygy telescope tion transit transits of Venus true anomaly velocity Venus vertical wire zenith distances