Ballet at the Sydney Opera House: Thinking about Slessor   At Interval we take our bubbly outside to the rain. The agile dancers cease and change, the panto team released from within Don Quixote’s stage mule Dancers in Stravinsky’s Rite of Spring will soon evoke Waterlilies, Indigenous and far from Paris, It’s red earth and didgeridoo.   A jet boat booms on its way to Manly. An older ferry turns in Harbour bright. A floodlight cups like a hand and gestures in upward beam the floating beads of rain that stream and drift across the white tile sails. It’s a…