What Did Ibrahim عليه السلام ‘s People Worship?
Before this incident starts, the verses 6:74-75 tells that Abraham had already declared his father and his nation wrong for their idolatry, and he had attained faith in one God by watching the system of heaven and the earth. His declaration was his way to lead his people to a conclusion they should reach. this is not a monologue but a public declaration as is evident by the statement I am free from you polytheism (6:78). Also, the same verse tells that these objects too, were deities of his nation. The matter of historical proof rest with the historians. However, we can assume that it was common in many nations that they worship celestial objects.