差分图像运动监测仪广泛应用于视宁度的实时测量.利用随机相位屏和光学离焦像差模拟差分图像运动, 分析了差分图像运动监测仪的测量准确度, 结果表明差分图像运动监测仪能够可靠地测量地面处湍流.在国家天文台兴隆观测站, 开展了两台相同硬件配置的差分图像运动监测仪的对比实验, 分析曝光时间的影响和测量结果的相关性.结果表明: 有限曝光时间降低差分图像运动, 使视宁度值测量值偏小;视宁度测量结果的时间变化趋势和统计结果一致性较好.

Differential image motion monitor is widely used to obtain real-time seeing. Differential image motion was numerical simulated by random phase screen and optical defocus aberration, and the measurement accuracy of differential image motion monitor was analyzed, which showed that differential image motion monitor can reliably measure the near-ground turbulence. Comparision of experiment of two differential image motion monitors with the same hardwares was carried out at Xinglong Station of National Astronomical Observatory of China. The correlation between exposure time and measuring results was analyzed. The results show that the limited exposue time will reduce differential image motion and underestimate seeing value, and the trends over time and statistics of measurement results have good consistency.