nocturnal vs star clock

nocturnal

noun
  • A device for telling the time at night, rather like a sundial but read according to the stars. 

  • A person or creature that is active at night. 

adj
  • Taking place at night, nightly. 

  • Primarily active during the night. 

star clock

noun
  • Synonym of nocturnal (“device for telling time”) 

How often have the words nocturnal and star clock occurred in a corpus of books? (source: Google Ngram Viewer )