深圳市天文台全天云图监测系统的设计与实现

摘要

全天云图监测对天文观测至关重要,目前大多数天文台站安装了实时云图监测相机,但共同的难题是如何在光线变化较大的情况下进行正确曝光.为解决这一问题,深圳市天文台自行开发了一套拍摄控制系统,根据相机可用的拍摄参数,计算得到曝光值索引曲线,采用0.3作为曝光值误差,在亮度变化较大的各种环境下进行正确曝光拍摄全天云图,并采用最大类间方差自适应阈值算法,对云进行有效识别.经多次测试,系统在亮度变化较大较快的环境下能拍摄到正确曝光的云图,为天文观测计划提供了极大的便利.%All-sky cloud monitoring is of key importance for astronomical observation. Most astronomical observatories in the world have all-sky cloud cameras now.But one common concern is to get accurate exposure in a vast range of illumination conditions. To solve this problem, Shenzhen Astronomical Observatory has developed independently an automatic exposure control system. By using the parameters of the all-sky camera, this system calculates an index curve of exposure value, with error of 0.3, to adjust the exposure of each picture that the camera captures. And based on the pictures with accurate exposure, cloud can be effectively detected by the maximum interclass variance adaptive threshold selection method. It has been proved in practice that this system works well in varying illumination changes,obtaining accurate exposure even in low-light circumstances,and therefore providing substantial convenience to observation planning.