A good place to start research is the
Talk.Origins Archive, an extensive library of counter creationist material. Of course, much of it has to do with biology and the like. Still, there are sections which have quite a bit of astronomy related material. The
Age of the Earth section includes several relavent entries, including:
There are more, but you get the idea.
Creationists come in all varieties. Most of those we encounter on the web are quite ignorant of science, but utterly convinced they must be right. It is important to understand the depth of that conviction. Even if you prove conclusively to a creationist that they must be wrong, they will usually not change their mind. They will simply retreat into the conclusion that your proof is irrelevant, because they
already know that you must be wrong. They have to believe that you must be wrong, because otherwise the entire edifice of their faith is shattered, and they will suffer anything before they give up on their faith. Debating creationists is certainly useless if your real goal is to change their mind. Debating creationists only makes sense if you are talking to the audience, or the lurkers who hang around here but don't post. And actually debating a creationist face to face requires refined debating skills, or you will look silly no matter how right you are.