From 1782 to 1802, and most intensively from 1783 to 1790, Herschel conducted systematic surveys in search of "deep-sky" or non-stellar objects with two , and telescopes (in combination with his favoured 6-inch-aperture instrument). Excluding duplicated and "lost" entries, Herschel ultimately discovered over 2,400 objects defined by him as nebulae. (At that time, nebula was the generic term for any visually diffuse astronomical object, including galaxies beyond the Milky Way, until galaxies were confirmed as extragalactic systems by Edwin Hubble in 1924.)