STARLAB.  Take a naturalist-led journey through the night sky in this portable planetarium.  Find out what constellations, planets and stars are on tap for this season.  For ages 5 and up.  1-2pm (two 25-minute sessions).  Chattahoochee Nature Center, 9130 Willeo Road, Roswell.  More info:  770-992-2055 or www.chattnaturecenter.org.