Herschel 400

The Herschel 400 is a list of 400 Galaxies, Nebula and Clusters taken from the catalogue of 2508 Deep Space Objects (DSO) compiled by the great 18th century astronomer William Herschel and his much loved sister Caroline, during the years  1783 to 1802. The list is made up of 231 Galaxies, 107 Open Clusters, 33 Globular Clusters, 20 Planetary nebula, 2 halves of a single Planetary Nebula and 7 Bright Nebula. It contains some of the best non Messier objects, as well as some faint objects which test the abilities of amateur astronomers equipped with a modest sized telescope.

Each member within Herschel’s list is prefixed by the letter H followed by a Roman Numeral which identifies the class of object to which it belongs,  and then an Arabic number indicating the order in which it appears in its class. The classification of objects devised by Herschel being: I (bright nebula); II (faint nebula); III (very faint nebula); IV (planetary nebula); V (very large nebula); VI (very compressed and rich clusters of stars); VII (pretty much compressed clusters of large or small stars); VIII (coarsely scattered clusters of stars).

The list was created by members of the Ancient City Astronomy Club (ACAC) of St. Augustine Florida, in response to a letter published in the April 1976 issue of Sky and Telescope magazine by James Mullaney who suggested that amateurs set up informal "Herschel Clubs" with the aim of observing the brightest objects in Herschel’s original Catalogue. The ACAC took up the challenge and after much discussion and debate came up with a final list of 400 objects, which they said, would challenge observers with telescopes larger than 6 inches that were affected by light pollution.

Since its inception the ‘Herschel 400’ has become very popular amongst amateurs and is a valuable addition to the Messier and Caldwell lists of DSOs. A ‘Herschel 400 Club’ is now part of the Astronomical League (AL), an organization composed of more than 240 amateur astronomical societies across the United States, which awards certificates to members who observe every object on the list. Such a certificate is considered by the AL to be a ‘prized possession amongst serious amateur astronomers as an indication of their advanced level of their amateur capabilities’.