南京大学65 cm反射式望远镜CCD相机的性能研究

Performance of the CCD Camera on the 65 cm Reflective Telescope at Nanjing University

2021年6月,使用南京大学本科实验教学的65 cm反射式望远镜系统,对其后端的电荷耦合器件(Charge-Coupled Device,CCD)的性能采用圆顶平场法进行了实际测定,得到了CCD相机的快门函数;同时用平场序列曝光,检测了CCD相机的线性。CCD相机的读出值从0到61900模数转换单位(Analog-Digital Unit,ADU)非线性小于1%,同时CCD相机的增益为1.02e^(-)/adu,读出噪音为13e^(-)。但对于恒星这样的点光源的观测,当像元的数值高于38000 adu时产生溢出。因此,在使用本CCD相机做点光源观测研究时,需要选择恰当的曝光时间,避免星像溢出。实际天文观测中,利用此研究得到的快门函数可以对观测图像进行校准,有效提高测光精度。

We have determined the capability of the Charge-Coupled Device(CCD)system by the dome flat field method on the backend of the 65 cm reflective telescope at the Zuodijiang Observatory of Nanjing University,and have obtained its shutter function.The response linearity of CCD camera has also been tested by the flat field exposure series.The results show that nonlinearity of the readout value is less than 1%from 0 to 61900 ADU,and the gain of CCD camera is about 1.02e^(-)/ADU,and the readout noise is about 13e^(-).However,overflow has occurred when the readout value is above 38000 ADU for point-source observation.Therefore,proper exposure time is needed to avoid star image overflow when using this camera for point source observation.In the future observation,this shutter function could be used to calibrate the image in order to improve the photometric precision.