Andrew Cooper
Jan 17, 2004    Sentinel, AZ (map)
46cm f/4.5 Deep Violet

Dim, low surface brightness, no apparent core beyond a slight brightening at the center, a dim 13.9 magnitude star just south of the core

Harold Corwin

IC 2133 = NGC 1961. Here is one of the objects that force me to ask the question "What was Bigourdan thinking?" He measured it twelve times on three nights, could not find NGC 1961 when he looked for it on one of those nights, and must have been aware that William Herschel's positions were subject to large accidental errors. So, how could Bigourdan believe that his "Big. 385" was a new object and not the one that William Herschel found?

Well, he obviously did because the object ended up in the 2nd IC. Dreyer discovered the identity a few years later when he prepared William Herschel's Scientific Papers for publication. There is no doubt about the identity, either.

So, "What was Bigourdan thinking?" (Obviously, a rhetorical question.) Also see NGC 1961 for the story of William Herschel's mistaken position.

― IC Notes by Harold Corwin

Harold Corwin

NGC 1961 = IC 2133 is another of the identifications that Dreyer himself made. He has the long explanation in a note in his 1912 edition the Scientific Papers; briefly, William Herschel's comparison star had incorrect coordinates in one of the catalogues that Caroline Herschel was using during the reduction.

When the right coordinates are used, William Herschel's position is still 22 seconds out, but the identity with Bigourdan's object (Big. 385 = IC 2133, which see) is certain. There is nothing else nearby that William Herschel could have mistaken for the galaxy.

― NGC Notes by Harold Corwin

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