On April 1 Cru is above the SCP at midnight and on Oct 1 Cru is below the pole at midnight so both methods work. I got the idea from Rumker who was at Parramatta in the 1820s. Earlier this year I visited his grave in Lisbon Portugal and cleaned it up so the writing on it is now readable. Brisbane employed Rumker as an astronomer but he walked out after a dispute and Dunlop took over.
See
http://www.austehc.unimelb.edu.au/fam/1524.html