Focus Measures Assessment for Astronomical Images

Precise focus is an essential step in astronomical research since an accurate measure of celestial objects properties depends on it. This paper presents a performance comparison of different focus measure operators. The focus operators are applied to five sequences of star-clusters observations. These sequences are observed using the 74-inch telescope of Kottamia Astronomical Observatory (KAO). Each sequence contains in-focus and out-of-focus frames. The experimental results show that the Normalized Variance has the least distance between the best overall score and least standard error.