 One problems was that many instrument makers including Herschel did not pass on their mirror making craft, and by the next century reflectors had largely been passed over in favour of small achromats (2 lens refractors).It was not until the 21st century that really large refactors would predominate once again.Some of the achievements in astronomy of the 19th century telescopes include the discovery of the planet Uranus, the Messier catalog, and overall increased detections of comets, stars, star catalogs, and other charting.