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AAOmega CCD information


Each arm of the AAOmega system is equipped with a 2kx4k E2V CCD detector and an AAO2 CCD controller. The blue arm CCD is thinned for improved blue response. The red arm CCD is a low fringing type. Both CCDs can be driven in a charge shuffling mode. Basic Nod+Shuffle support is provided by default, more complex modes will require liaison with support staff in advance of any proposal.

CCD operational information is listed below. Some important considerations planning AAOmega observations are:

  1. Single amplifier (right amp.) is currently the default mode of operation, pending full commissioning of the dual readout mode.

  2. In the blue, and particularly at high resolution or during dark of moon, observations can become read noise limited if integrations are short. Hence longer exposures may be required and the slower read-out modes should be considered.

  3. Saturation changes with the changes in gain encountered in different readout modes. In the high gain (faster readout) modes saturation occurs somewhat below ~65,000 counts.

  4. Ultrafast mode is very noisy, due to the high readout rate, but it is believed to produce valid observations. While further study of this mode is still required, programs that could utilize such a rapid read-speeds should discuss the options with AAOmega support staff in advance of proposal preparation.

  5. The CCDs can be windowed to reduce readout times, broadly in proportion to the size of the reduced window. Note that unused pixels will generally still need to be clocked through the CCD, although this rate is faster than the digitization speeds given below.

Parameters for the AAOmega Blue E2V CCD

Dark 1.4 e/pix/hr (after post power up stabilization, 4hr)

Left Amp Right Amp
Read time Gain Read Noise Gain Read Noise
Sec e/ADU e e/ADU e
Ultrafast 21 4.608 7.06 4.494 6.77
Fast 75 2.890 4.76 2.789 4.44
Normal 120 1.921 3.83 1.848 3.81
Slow 145 1.164 2.89 1.13 2.86
Xtraslow 403 0.278 2.29 0.27 2.18

Parameters for the AAOmega Red E2V CCD

Dark 1.01 e/pix/hr (after post power up stabilisation, 4hr)

Left Amp Right Amp
Read time Gain Read Noise Gain Read Noise
Sec e/ADU e e/ADU e
Ultrafast 21 4.541 7.22 4.6 7.0
Fast 75 2.708 4.68 2.803 4.53
Normal 120 1.788 3.76 1.799 3.49
Slow 145 1.098 2.83 1.119 2.62
Xtraslow 403 0.277 2.36 0.272 2.02

Sarah Brough (sb@aao.gov.au)