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Detector

The default detector used by AF2 with the WYFFOS Long Camera is Red+4. However, it is also possible to mount its predecesor WHTWFC , if there is a strong scientific case that justifies its use.

Red+4 suppresses the fringing at the red end, being <1% at 850 nm, versus the ~30% that WHTWFC shows at the same wavelenght. As well, Red+4 is cosmetically superior to its predecesor, as this one has been degraded for many years of use. Also being a 4k x 4k chip is also a plus, as none fibre is lost in the gap as it happens with WHTWFC.

Red+4

Red+4 is an e2v 231-84 4k x 4k, red-sensitive, fringe-suppression CCD, which has been successfully commissioned in semester 2013A.See commissioning report here.
The mosaic has a useful area of 4096 x 4112 pixels of 15 micron each.

Binning is allowed, and two readout speeds are offered:

  • slow (readout-noise = 4.2 e-)
  • fast   (readout-noise = 5.6 e-)

Read-out plus disc-writing times (sec) for different binning setups:

binning 1x1 2x2
SLOW 50 39
FAST 18 15


Sketch of fibres and CCD layout
Figure 1. Sketch of the Red+4 layout, together with information on the orientation of spectra and fibres.


WHTWFC

WHTWFC is a blue-sensitive 2-chip EEV mosaic, which has been in use since 1999.
The mosaic is usually windowed and mosaiced so as to have 4300 x 4200 pixels, 13.5 microns each.

Binning is allowed, and two readout speeds are offered:

  • slow (readout-noise = 4 e-)
  • fast   (readout-noise = 6 e-)

Read-out plus disc-writing times (sec) for different binning setups:

binning 1x1 2x2
SLOW 40 15
FAST 30 10


Sketch of fibres and CCD layout
Figure 2. Sketch of the WHTWFC layout after windowing, together with information on the orientation of spectra and fibres.


Note that 2 fibres (usually #82 and #83 or #83 and #84) are lost in the gap between the two chips.



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Contact:  (AF2 Instrument Specialist)
Last modified: 22 September 2015