Popular Astronomy, Volume 50

American amount appeared astronomical atmosphere average beginning body brightness changes College comets complete correction course craters curve determined direction distance earth eclipse effect equal errors fact fall field figure fireball galaxies give given height important included increase indicated interest July June known later length less light magnitude March Mare Imbrium Mars mass material maximum mean measured meeting meteor meteorite method Michigan miles minutes month moon motion moving Name nearly Notes novae object observations Observatory obtained occur original parallax path perhaps period photographs planet position possible present probably problem published reached recent recorded reference region reports rotation seems seen Society solar Standard stars suggested surface Table telescope tion train University variables variation visible