In the Star Walk 2 app, the grey orb icon is typically used to represent the Moon when it is in a phase where minimal to none of its surface is illuminated by the Sun from the perspective of the Earth, such as a new moon or a nearly new moon phase. During these phases, the Moon isn’t visible against the night sky, yet its presence can be important for people observing other celestial phenomena or planning stargazing, as a less illuminated sky provides darker skies for clearer observations of stars and planets. This icon assists users in identifying the Moon’s position despite its lack of visibility, allowing for a more comprehensive understanding of the night sky.