Is there an entry fee ?

Yes, there is. The entrance fee is very inexpensive ($8 adults, $4 children). The planetarium is an extra fee. However, the museum alone has a lot too see, so we didn't even bother with the planetarium. See link for posted posted fees and visitors info: http://museum.unl.edu/museum_info/index.html

Yes, it is around 8 per adult. 4 for kids. But well worth it if you enjoy that type of history!