Popular Astronomy, Volume 57

American angle appear asteroid astrolabe Astronomical Society atmosphere atomic average bright brighter California Cepheids cloud color comets crater curves determined diameter distance earth eclipse enstatite Ephemeris fireball galactic galaxy globular clusters Harvard Harvard College Observatory heliometer indicated instrument interest July June Jupiter latitude Lick Observatory light lunar magnitude Mars mass maximum mean measured meridian Messier meteor meteorites Meteoritical Society method miles Milky mirror month moon motion nebulae Notes novae object observations Observatory OCCULTATIONS VISIBLE October Open cluster optical orbit origin Palomar Palomar Observatories paper parallax particles period photographic planetary planetary nebulae planets plates POPULAR ASTRONOMY present probably published radiation radio relative rocket rotation Russell Santa Rosa Saturn scientific solar system space spectra spectrum stellar Struve Sunspot Table telescope temperature theory tion University Uranus Variable Star velocity Venus Yerkes Observatory