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The letters IC with a number.
Also known as: IC number, IC supplement designation
The designation of an object in the Index Catalogue, the supplement issued to extend the New General Catalogue.
Designates an object in the Index Catalogue, issued as a supplement to the New General Catalogue.
Contexts: History
Exists because photography found far more objects than visual observation had, so the supplement records a change in instrument rather than in the sky.
Contexts: History
Two capital letters followed by a number, distinguished from the NGC designation by having one letter fewer.