Harold Corwin

IC 1657 = IC 1663. Here is another case where Swift has rediscovered one of his own galaxies -- just seven weeks later. On 4 Sept 1897, he found a nebula which he described as "eeF, S, eeE, a ray; no sts near." There is such an object about 20 seconds preceding, and 0.7 arcmin north of his position; we can confidently assign the number IC 1657 to this. 20 second (or more) RA errors are common in Swift's lists.

His second position, from 30 Oct 1897, is not as good. It is 2 minutes of time too large, and 2 degrees too far north. But he provides us with a more detailed description: "eeF, vE 350 deg; 5 sts sf, 3 have distant companions." This fits the nebula and the neighboring stars very well, too. Since there are no other galaxies in the area that fit this description, and since the position errors are digit errors, the identity is all but certain.

Dreyer has another possible declination (30 arcmin south) for IC 1663 in the summary description. This comes from Swift's "5th Catalogue" of nebulae found at Lowe Observatory. Swift published these in several different places, and collected them all in a long list -- which Dreyer called "Swift XI" -- in AN. The shorter lists sometimes have more detailed descriptions, while the longer one occasionally has slightly revised positions (not that they help much ...).

In this case, the declination published in the fifth list is a probably a typo as the long list position is just two degrees off (rather than 1.5 deg). This is, in fact, what caught my eye as I first tracked down IC 1663 during preparation of SGC: the minutes of declination are almost identical for both entries in the long list.

A final comment: Swift's 11th and 12th "catalogues" (his final two lists), those with the nebulae that he found at Echo Mountain, contain more errors than his earlier lists assembled at Warner Observatory in Rochester, NY. By the time he made these observations, his eyesight was beginning to fail, and he was often distracted by having to show tourists around the observatory. I suspect that these two factors alone contributed to his increased error rate.

― IC Notes by Harold Corwin

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