WATCH TUTORIAL HERE : http://www.youtube.com/watch?v=LsXneaz-U6g
Its very simple to use, simply press play!
All the layers are well organised and grouped according to the size of the star.
You have the ability to use only a specific size star by turning off the visibility of layer groups, change the opacity of the stars glow, move layers around, duplicate layers to make more stars and many other possibilites.
The action also creats an optional nebula feild which is editable. You can easily change the colors and choose what areas of the clouds you want visible.