Automatic data analysis for the Sky Brightness Monitor

The Sky Brightness Monitor (SBM) is an important instrument for measuring the brightness level for the sky condition, which is a critical parameter when judging a site for solar coronal observations. In this paper, we present an automatic method for processing SBM data in large quantities. This method can separate the regions of the Sun and the nearby sky, as well as recognizing the regions of the supporting arms in the field of view. These processes are implemented on the data acquired by more than one SBM instrument during our site survey project in western China. Applying the result from our processes, an analysis has been carried out for the assessment of the scattered-light levels by the instrument. These results are considerably significant for further investigations and studies, notably to derive a series of other atmospheric parameters, such as extinctions, aerosol content and precipitable water vapour content, that are important for candidate sites. Our processes also provide a possible way for full-disc solar telescopes to track the Sun without an extra guiding system.