The Herschel 400 is a list of 400 celestial objects compiled by astronomer William Herschel in the 18th century. It includes a variety of galaxies, star clusters, and nebulae, making it a valuable resource for amateur astronomers. The list is designed to help observers explore the night sky and discover deep-sky objects. This collection is particularly popular among amateur astronomers because it features objects that are visible with small telescopes. The Herschel 400 serves as a stepping stone for those looking to expand their observational skills and knowledge of the universe beyond the brighter stars and planets.