Harold Corwin

IC 2555 = NGC 3157. The IC position, from an Arequipa Bruce plate examined by Delisle Stewart, is good. But the NGC position is 30 arcmin off.

Curiously, John Herschel's original position in his CGH Observations is correct. It turns out that in precessing and transcribing the position to the GC, either John Herschel or one of his assistants made a 30 arcmin error in the declination. Dreyer faithfully copied the mistake into the NGC.

One other curiosity exists with John Herschel's records of this galaxy. He has only a single observation from sweep 535 on 28 Jan 1835. He looked for it a second night (sweep 678 on 16 Feb 1836), but has no position recorded and the odd note, "Looked for but not found by this. However, no RA is noted, perhaps it was looked for too late. The obs of S[weep] 535 is positive, and correctly reduced." This tells us that John Herschel hoped to make a second observation of the object, but somehow missed it. In any event, his problem was apparently in RA, not Dec as later crept into the GC and NGC.

― IC Notes by Harold Corwin

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