Why does the Satcharitra compare Sai Baba to the sun and the moon?

Actually, the Satcharitra uses these comparisons to illustrate Sai Baba's superiority over them. Chapter 50 explicitly states that it is not fitting to compare him to the sun, because the sun sets, implying a limitation that Sai does not have. Similarly, the text notes that if one compares him to the moon, the moon wanes, whereas Sai is described as being 'forever complete.' Therefore, these comparisons are made not to show similarity, but to highlight that Sai transcends the limitations of even the most powerful celestial bodies, emphasizing his eternal and perfect nature.