watcher

Noun

• a person who keeps a devotional vigil by a sick bed or by a dead body

• a guard who keeps watch

• a close observer; someone who looks at something (such as an exhibition of some kind)
  • the spectators applauded the performance
    
  • television viewers
    
  • sky watchers discovered a new star
    

Related words

• Synonyms: 
  watchman , security guard , spectator , witness , viewer , looker