The Index Catalogue
The Index Catalogue (IC) is a key astronomical reference featuring 5,386 deep-sky objects, including galaxies, nebulae, and star clusters. Compiled by Danish astronomer John Louis Emil Dreyer, it serves as the official supplement to the larger New General Catalogue (NGC).
Published in two volumes—IC I (1895) containing 1,520 objects and IC II (1908) with 3,866 objects—it encompasses discoveries made between 1888 and 1907. Many of these objects were identified using the then-new technique of long-exposure photography, enabling the detection of fainter celestial bodies beyond the reach of earlier visual surveys.
