Why do these two images not wanna go on top of each other?

Question

http://lucasdebelder.be/googledoodle/

I want to have the planet (bottom image) on top of the top image (the blue background/space). I have a main div class:"center" set on 'position: absolute' and around both of those images is separately a div wrapped with position: relative; but somehow they don't want to go and sit on top of each other, I've also tried it with z-index but that doesn't work either.

Thanks in advance.

Answer 1

Use these properties the planeet_achtergrond class:

.planeet_achtergrond{
  position: absolute;
  bottom: 150px;
}