opera glasses vs spotting scope

opera glasses

noun
  • One or more pairs of small low-powered binoculars for use by members of the audience at a theatrical performance. 

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