Observational Hobbies

People who enjoy pursuing an observational hobby do so in order to track, spot or watch certain things. For example, amateur astronomers enjoy watching the sky and tracking asteroids, monitoring variable stars, and discovering transient objects, such as comets, whilst trainspotters make an effort to 'spot' all of a certain type of rolling stock (e.g. a particular class of locomotive). In the course of pursing their hobby, most observational hobbyists become highly knowledgeable about their subject.