选址与日冕观测组知识库

现代日晕光度计是用于精确测定日间天文监测址点多种大气参量的精密仪器,它已列为我国西部太阳设备选址工作中的重要设备之一。在数据处理中日心坐标的选取对处理结果有决定性影响,但由于观测过程中日面中心坐标在图像上随时间变化,因此发展了两种用于日面中心自动定位的方法:日面总强度法和傅里叶变换相关法。详细介绍了这两种方法,并对比取得的结果差别及其对测量结果的影响。

A modem Solar-Halo Photometer (SHP) is a precision instrument used to measure various atmospheric parameters for astronomical day-time observation sites. Such an instrument plays a key role in our solar-observation site survey program in the west China. The instrument takes the photometric measurements of muhiple wavelength bands. The accuracy of locating the solar-disk center can decisi'~ely affect the photometric results. The solar-disk center in an SHP image varies with time because of imperfect observation conditions. With fast increasing SHP data, there is a strong need to automatically reduce the data. Here we develop two automatic methods for locating the solar-disk center coordinates: the total solar-disk intensity curve method and the Fourier-coefficients correlation method. The first method searches for the maximum of the variation curve of the total solar-disk intensity, which is taken as the solar-disk center in the image. The second method searches for the most significant correlation b~;tween the Fourier coefficients of a mask of the solar-disk and the recorded image. We have compared the solar-disk coordinates obtained by these two methods and find that the results are very close, showing the two methods are consistent and either one can be used. With the two methods we will be able to reduce SHP data in future analyses.