近地天体望远镜的PSF分布研究

Distribution of PSF of Near Earth Object Survey Telescope

盱眙近地天体望远镜CCD视场为1.94°×1.94°,作为大视场望远镜由于存在场曲现象,因此根据单颗星像调焦会导致PSF(Point Spread Function)分布不均匀.研究所拍摄图像的PSF分布特征,并通过拟合半高全宽和离焦量的函数关系模拟出弯曲焦面,从而确定出最佳成像平面.制定出根据PSF的半高全宽直方图来判断最佳成像平面的调焦方法.

The field of view of CCD in NEOST（Near Earth Object Survey Telescope）is 1.94°×1.94°.As a wide-field telescope,the focusing according to single stars leads to uneven distribution of PSF（Point Spread Function）due to the field curvature.The contour map of PSF＇s FWHM（Full Width at Half Maximum）indicates the features of the distribution of PSF.The focal surface is yielded by fitting the relation between defocus and PSF＇s FWHM. It is confirmed that the focal surface reshaped by the field lens is not flat but convex,and the distance from the peak to the valley is about（85±5）μm.The center of the distribution of PSF deviates from the CCD center.This phenomenon is considered to be caused by the inclination of CCD.The method of getting the best-focus can be found by using the histogram of PSF＇s FWHM.