2.1. CCD camera head
As described above, the stability of the CCD camera is a critical factor in measuring the absolute brightness. A fluctuation in the temperature of the CCD chip will cause uncertainty in the zero point of the photometric system, and its sensitivity.
We have employed a liquid-N2 cooled CCD chip (EEV CCD 42-80) with a compact de-war 1 kg) for WIZARD. The chip has a huge imaging area (27.6x55.3 mm), 2048x4096 pixels, as well as high sensitivity (90% at 500 nm). Since our previous CCD chip was cooled electronically, that system was consequently subject to the unclear temperature
Figure 2. Transmission of the filter. The peak wavelength and FWHM are 480 nm and ~45 nm respectively.
variation. Dark noise of the new chip will be negligible. Also, the readout noise will be significantly reduced by adopting an excellent device control system; C0GIT03 . At 190 K, measured readout noise and dark current is 20 e~ and <Cl e~ respectively.
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