Harold Corwin

NGC 1730 = IC 2113. This is one of the bright Leander McCormick nebulae that the Herschels could probably have picked up. However, it was apparently first seen on 12 November 1885 by Francis Leavenworth.

It is one of the rare nebulae in the first LM list to have more than a single observation, but its position is still given to only a full minute of time.

It is also one of the few to have two sketches from LM -- the first is Leavenworth's discovery sketch, the second is by Frank Muller from 16 February 1887. The sketches are similar, but Leavenworth claims two nebulae, while Muller -- correctly -- has a nebula with a superposed star. Leavenworth's measurement of the separation (10 arcsec at PA = 110 degrees) is, however, correct. The star can be easily seen in the 2MASS image superposed just a few arcseconds northwest of the nucleus of the barred spiral, within the inner ring.

By the way, the NGC misattributes the object to Ormond Stone rather than to Leavenworth.

In between the two LM observations which led to the sketches, Lewis Swift picked up the galaxy on 9 October 1886 and published it in his fifth list of new nebulae from Warner Observatory in Rochester, NY. His position for the galaxy is one of the best he ever published, falling just a few arcseconds from the nucleus (statistics suggests that this happens now and then). Fortunately, Dreyer used this position for the NGC.

Well, OK, you say, but what about IC 2113? That was found by Barnard and is apparently one of the several discoveries that he sent directly to Dreyer. I find no trace of it in any of his papers on nebulae, at least in those papers that I've collected. His position for the galaxy is nearly coincident with Swift's, so I have to assume that neither he nor Dreyer checked the NGC closely.

Comparison stars for this also figure in the uncertain identifications for IC 400, which see.

― NGC Notes by Harold Corwin

Drawings, descriptions, and CCD photos are copyright Andrew Cooper unless otherwise noted, no usage without permission.

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