Popular Astronomy, Volume 51

altitude American angle appears asteroids Astronomical Society ataxite atmosphere August brighter brightness catalogs celestial colour comet Copernican Copernicus Cygni December determined diameter distance Earth eclipse Ephemeris equinox error estimates explosion eyepiece fall February feet fireball given Goodsell Observatory Greenwich Harlow Shapley Harvard Harvard College Observatory January Jupiter latitude light curve longitude lunar magnitude March Mare Imbrium Mars mass mathematics maximum meteorite method miles Moon Moon's motion navigation nebulae Notes Nova object observations obtained occultation orbit OTERMA parallax path period photographic planet plates Pleione POPULAR ASTRONOMY position present probably Professor proper motions reports rotation Saturn SCRIPTA MATHEMATICA seen siderites solar spectral spectral type spectroscopic sphere SS Cygni stellar surface telescope theory tion Tucson University Variable Star velocity Venus visible visual visual magnitude volume