Hi Carol 
 Have you tried looking at the records of the NSW Births, Deaths & Marriages?  I had a quick look and found a death entry for "Ernst Raubitschek" in 1971. I'm not sure if it's the same person, without ordering a copy of the Certificate. But looking at the Electoral roll in 1980 it only shows Fredericke at the address you mentioned in Pymble.  There is also an entry for "Gertrude Raubitschek" in the BDM records for 1987 but I'm not sure if that's any relation since she is shown as being 84 at the time of her death (so born approximately 1903). I also came across a video recording relating to a lady "Fritzi Raubitschek" from the Shoah Foundation: https://vhaonline.usc.edu/viewingPage?testimonyID=12495   There are others mentioned in the recording (including the family Pracht), but I'm unsure if there is any relation. They are shown as living in Pymble.  If you are aware of whether they practised their faith, one of the local shuls may have a Book of Remembrance. All the best with your research.

Bronwyn Van Dam