refractor vs spotting scope

refractor

noun
  • A refracting telescope. 

  • anything which refracts light, heat or sound 

spotting scope

noun
  • A compact high-power monocular telescope optimized for detailed observation of distant objects such as wildlife or the strike of a bullet on a target. 

How often have the words refractor and spotting scope occurred in a corpus of books? (source: Google Ngram Viewer )