IO:O was originally equipped with a Fairchild 486 CCD detector. However, this was found to have degraded during storage resulting in poor blue Quantum Efficiency (QE), so it was therefore replaced in June 2012 with an e2V CCD 231-84. This has worked well giving broadly similar performance to RATCam but with the advantage of a wider field of view. Read noise is currently slightly higher than RATCam with QE tilted more towards the red end of the spectrum. At present a single readout mode is implemented, giving a readout time of 18.5 seconds (2x2 binned). 1x1 binning is also available, although we do not regularly obtain 1x1 flats. Please contact the LT Support Astronomer if you wish to use this mode.
IO:O is equipped with a large diameter Uniblitz iris shutter. This results in a different exposure time between the centre and edges of the field of 80ms. For reasonable photometric accuracy exposure times should therefore be greater than 20 seconds. Please feel free to discuss this issue with the LT Support Astronomer should you require short exposure times. It is of course possible to defocus the telescope so that bright targets can be observed.
IO:O's other specifications are listed below.
Detector: 4096x4112 pixel e2v CCD 231, deep depletion, Astro ER1 coated
Pixel size: 15.0 x 15.0 microns
Pixel scale: approx. 0.15 arcsec/pixel (unbinned)
Field of view : 10 x 10 arcmin
Read noise: < 8 electrons
Dark current: < 0.002 e / pix / sec (unbinned, 263K)
~ 0.01 e / pix / sec (unbinned, 273K)
Binning: 1x1 and 2x2
Readout time1: ~37 sec (1x1 binned), ~13.5 sec (2x2 binned)
Windowed modes: Not currently available
Bad pixels: 6 dark point defects; 2 hot pixels; 1 column defect. (pixel mask)
Gain (1x1): 1.6 electron / ADU
Gain (2x2): 1.6 electron / ADU
Quantum Efficiency (figures supplied by manufacturer)
Wavelength(nm) Quantum Efficiency(%)
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