optical telescope vs spotting scope

optical telescope

noun
  • An instrument, used both for recreational and scientific purposes, which provides a magnified view of distant objects by collecting and focusing light by means of mirrors and/or optical lenses. 

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 optical telescope and spotting scope occurred in a corpus of books? (source: Google Ngram Viewer )