NGC vs New General Catalogue

NGC

New General Catalogue

name
  • A catalogue of deep sky objects compiled in the 1880s by J. L. E. Dreyer using observations mostly from William Herschel. It contains nearly 8,000 objects, known as the NGC objects. Objects in the catalogue are numbered, and the letters NGC are prepended to these numbers, as in NGC 224 (the Andromeda Galaxy) or NGC 6205 (the globular cluster in Hercules). 

How often have the words NGC and New General Catalogue occurred in a corpus of books? (source: Google Ngram Viewer )