WHAT WE KNEW THEN by Klaus Brasch Just Over a Century Ago RO B E R T BA LL , A P OPUL AR GUIDE TO THE HE AVEN S (19 0 4) / PU B LIC D O M A IN (15) What could the reading public know about astronomy in 1900? 58 D EC E M B E R 2 019 * SK Y & TELESCOPE