celestial sphere vs circlet

celestial sphere

noun
  • An abstract sphere of infinite radius which serves as the imaginary backdrop for celestial objects, and of which the visible sky is one hemisphere. 

name
  • the figure of the universe as an imaginary sphere whose center is the Earth 

circlet

noun
  • A round body; an orb. 

  • A crown without arches or a covering. 

  • A ring (typically of gold or silver) worn as an ornament on the head. 

  • A small circle. 

How often have the words celestial sphere and circlet occurred in a corpus of books? (source: Google Ngram Viewer )