A Treatise on Astronomy

61 Cygni altitude angle aphelion apparent diameter apparent motion appear asteroids astronomers binary stars body bright called centre circle comet computed conjunction constellation declination density determine difference diminished direction disturbing force diurnal motion double stars earth earth's orbit eccentricity eclipse equal equator fixed stars full moon gravity heavens height Hence horizon horizontal parallax inclination increased inequality inferior conjunction inferior planet interval Jupiter latitude less light limb longitude magnitude Mars mass mean distance Mercury meridian millions of miles moon's move naked eye nearly nebula Neptune node nucleus observations parallax passes perihelion period planet pole portion position radius refraction represent revolution revolve right ascension ring rotation satellite Saturn seen semi-diameter shadow sidereal solar system spots sun's attraction sun's disc superior planet supposed surface synodical period tail tance telescope tidal wave tide tion transit Uranus velocity Venus visible zenith