According to personal experience, the written test will not have too difficult astronomical questions (too simple compared with astronomical olympiad), but also some questions to examine the comprehensive quality.
The interview should be a group interview (as I was). People who are familiar with astronomy can indeed have certain advantages, but more is to examine your language expression ability and whether your thinking is divergent and flexible enough through interviews.
Now there is not much time from the astronomy summer camp, and the surprise attack may not have a good effect.
Personal advice:
1. Buy a simple astronomy textbook (such as concise astronomy course and basic astronomy) and have a basic understanding of astronomy. The Olympic guide is also a good book. )
2. Buy an introductory book on observation (stars and planets, teach you to look at the stars), or download some electronic star maps to learn about our starry sky, which may stimulate your interest in astronomy.
3. Join some astronomical Q groups, and it is best to take part in some observation activities.