Describe symbolism in Shooting the Moon by Frances O'Roark Dowell

TJ is always taking moon pictures. He says that he is fascinated by the moon and its secrets, which is why he is always shooting pictures of it. When he goes to Vietnam he continues to shoot moon pictures. Jamie prints these moon pictures and Cindy hangs them all over her bedroom walls. By the time TJ goes missing in Vietnam, Cindy's walls are pretty much covered in the moon photographs.