During our class time with Ron Cody he explained his theology that the stars, moon, and sun are signs of His Godhead (the trinity of God) as follows: "The sun represents the Father. He dwells in the light to which no one can approach. The moon is a sign of the Son of man. When you look at the moon you see the sun's reflection. Lastly, the stars typify the Holy Ghost, which is always multiple."
Also, the Bible records many miracles that Jesus did for the purpose of a sign to believers. John 20: 30 & 31 tells us that these miracles are a sign to keep believing and have life. Jesus did many other miraculous signs in the presence of his disciples, which are not recorded in this book. But these are written that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name.