The Bigger List
The NGC dwarfs Messier's catalogue by a factor of roughly seventy — and inherits all his messiness, then some.
The general catalogue that followed, an order of magnitude larger and far less tidy.
From 110 to 7,840
Charles Messier's list of things to ignore topped out at 110 objects. The New General Catalogue of Nebulae and Clusters of Stars — the NGC — lists 7,840. The jump in scale was made possible by two things: better telescopes and one uncommonly systematic family.
John Louis Emil Dreyer, a Danish-Irish astronomer working at Armagh Observatory in the 1880s, assembled the NGC from a mountain of prior observations, but the mountain was mostly made by the Herschels. William Herschel had spent years sweeping the sky with large reflectors, dictating descriptions to his sister Caroline while she logged them. His son John continued the work and extended it to the southern hemisphere from the Cape of Good Hope. Dreyer synthesised all of this — plus observations from dozens of other sources — into a single catalogue published by the Royal Astronomical Society in 1888.
The result was enormous, unwieldy, and immediately indispensable. Dreyer followed it in 1895 and 1908 with two supplements — the Index Catalogues, IC I and IC II — adding roughly 5,000 more objects. The NGC plus both ICs still forms the working vocabulary of visual deep-sky observing. Ask an observer what they were looking at, and the answer will almost certainly carry one of those two prefixes.
Dreyer followed it in 1895 and 1908 with two supplements — the Index Catalogues, IC I and IC II — adding roughly 5,000 more objects.
What the numbers don't tell you
Dreyer's catalogue is ordered by right ascension, the celestial equivalent of longitude, so the numbers run roughly west to east across the sky as it was measured in 1860. That is useful if you are sweeping methodically; it is useless if you want all the galaxies in Virgo in one place. Object type, constellation, apparent size, surface brightness — none of these are reflected in the number. NGC 1 is a faint galaxy in Pegasus; NGC 7840 is no more special than anything around it. The numbering was a filing system, never a guide.
That disorder comes with a second problem: Dreyer was only as good as his sources, and his sources were not always sure what they had seen. Double stars were logged as nebulae, non-existent objects crept in from misread coordinates, and several pairs of entries describe the same object twice. More than a century of subsequent checking has cleaned up much of this, but some NGC entries remain genuinely ambiguous. The catalogue is large enough to be comprehensive and messy enough to keep researchers honest — which, for a list compiled from nineteenth-century handwritten logs on two continents, seems about right.