a kind of refracting telescope (refractor) like the one used by Galileo Galilei
a refracting telescope in which the eyeglass is a concave in place of a convex lens, as in the most popular opera cup. It was the building originally adopted by Galileo, the creator of the tool. It shows the things erect, which, inside their natural jobs.
a type of refracting telescope which no more used in astronomy