What astrolabe symbol is the circle slash?

The circle slash is not an astrolabe symbol. In astrolabes, symbols are often used to indicate the position and motion of celestial bodies. For example, the sun is usually represented by a circle, the moon by an arc, Venus by a five-pointed star and Jupiter by a big plus sign. These symbols help to clearly mark the position of each celestial body on the astrolabe. But the diagonal line is not a symbol used to represent a specific celestial body, so there is no such symbol in the astrolabe.