In 2014 the AAOmega red CCD was replaced with a new, red sensitive E2V chip. The exposure time calculator linked below has not been updated to reflect this change.

The plot below shows the total system throughput observed before (dashed line) and after (solid line) the CCD upgrade. The plot can be used to understand how signal-to-noise ratios will improve over the estimates provided by the exposure time calculator. 

AAOmega Throughput with old and new red CCD

The AAOmega Exposure Time Calculator