||During the years from 1758 to 1782 Charles Messier, a French astronomer compiled a list of 110 diffuse objects that were difficult to distinguish from comets through the telescopes of the day. His aim was to catalog the objects that were often mistaken for comets. The Messier number is in the order of discovery. A thumbnail version of these objects are shown in Figure 01 (from left to right, and from top to bottom).
There are many repositories for keeping information of astronomical objects. The New General Catalogue (NGC) and Index Catalogue (IC) are other frequently quoted references for astronomical objects besides the Messier (M). IRAS refers to the Infrared Astronomical Satellite Archive. The Abell Catalog (A) is a list for clusters of galaxies, and 3C refers to the third Cambridge Catalogue for radio sources, ...