Enter magnitude in selected filter

Notes on the exposure time calculator

Magnitudes are in the Johnson system. All grating efficiencies assume they are used at the most efficient angle for that band, except 580V and 385R which assume a blaze of 4800Å and 7250Å respectively.

Sky subtraction can be either with 20-30 dedicated sky fibres (~1% sky subtraction accuracy), or with ~200 targets in nod & shuffle beam-switching mode (~0.1% sky subtraction accuracy), or with ~100 targets using nod & shuffle cross beam-switching mode (~0.1% sky subtraction accuracy). Mini-shuffling doubles the number of targets in nod & shuffle modes, with ~0.3% sky subtraction accuracy.

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