What do the three red lines in the astrolabe represent?

Important astronomical phenomena. The three red lines in the astrolabe refer to the red dotted line, red solid line and red diagonal line. When three red lines pass through the astrolabe, it represents an important astronomical phenomenon, the red triangle, also called the big triangle. The astrolabe is an important astronomical instrument used by ancient astronomers, astrologers and navigators for astronomical measurement, and it is widely used.