The Temporal Distributions of Good Imaging for the Spectroheliograph at the Yunnan Observatory

The durations of good imaging within a fixed year are preliminarily obtained by statistical analysis of imaging quality obtained from spectral observations in 1982 with the horizontal spectrograph installed at the Yunnan Observatory.The results show that in the Autumn,September and August,a good image is usually available.For a daytime,there are two time intervals during which the solar image is relatively better than other time,one is in the morning 2～3 hours after the Sunrise;another in the afternoon 3～4 hours before the Sunset,and it lasts about 0.5～1.0 hours for each.