It's excellent to see this on HN. Sun Ra and the Arkestra's genres transcend space and time, and their discography is massive, so it can be hard to tell people where to start listening, but "Jazz in Silhouette" (1959) is fine introduction to their more traditional style that won't startle you if you don't listen to much free jazz. In fact I just threw it on the ol turntable. If that tickles you, try "Space is the Place" (1973) on for something more experimental. In between, you cannot go wrong with the "Heliocentric Worlds of Sun Ra" albums (1965)