optical telescope vs theodolite

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. 

theodolite

noun
  • A surveying instrument, consisting of a small mounted telescope, used to measure horizontal and vertical angles. 

How often have the words optical telescope and theodolite occurred in a corpus of books? (source: Google Ngram Viewer )