天文台使用的液氮冷却的CCD照相机,多数是24h保持冷却状态的.由于种种原因,上海天文台的1.56m望远镜上的CCD照相机并非如此,只能每次观测前开始液氮冷却.按照文献记述,使用液氮冷却的CCD照相机,在达到指定温度后,至少再过2h性能才能稳定.1.56m望远镜的#1CCD照相机使用的是与众不同的Lick天文台的控制电路,对其性进行了测试.结果表明bias的图案在达到给定温度后就已稳定,但其平均值要在达到给定温度后3h才能稳定.而要使平场真正稳定到≤0.2%,需要在温度稳定后的4h.如果CCD工作时突然断电,其结果有随机性.一次试验表明,短暂断电后6min,bias和平场都能恢复正常;但另一次试验表明,断电后的bias和平场都稳定在另一种状态,不能恢复到断电前的情况.%Contrary to the majority of CCD cameras in the world, the #1 CCD camera of our 1.56m reflector is not filled with liquid nitrogen for 24h a day due to some practical difficulties. According to the literature, even the given temperature of the CCD is arrived, the performance of the CCD camera can only be stabilized two hours after. The controller of #1 CCD comes from the Lick Observatory, and how long it should be waited for this special camera has been tested. In addition, if the CCD camera is suddenly turned off and on again, can the performance of the CCD keep stable? Some tests in these respects were completed. The results are: the pattern of the bias becomes stable when the given temperature is arrived, but its average value becomes stable after 3 hours, and after 4h the variation of the flat field is less than =0. 2% . When the CCD camera is suddenly turned off and on again, it gives random results. One test has shown that both the bias and flat field can recover their previous state after 6 minutes; but another test has shown that the bias and flat field changed to other stabilized state and never returned.
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