Harold Corwin

In March 2017, Gary Kronk found the star field that Swift described in his 12th list for this object. Here is Swift's full description, "eeF, lE, v small. 3 B sts in line n, also circle of sts n. Saw it twice, failed once." The star field suggests that Swift saw a double star south of the "circle of sts n". In particular, this entry in his list is almost certainly NOT a re-observation of IC 2974 as I had so confidently stated years ago.

The double star I've chosen is about five arcminutes south of the circle. It looks faint at first, but the combined G magnitude (from the Gaia DR1 list) is 14.4, well within Swift's capabilities with his 16-inch refractor. There is also the possibility that his object is the double star on the south side of the circle itself. This is brighter, but the brighter star is fully as bright as the northern star of the circle. I don't think that its fainter companion to the northwest would have given it enough of a nebulous hint on a poor night. So, this brighter double gets a question mark while the fainter one to the south carries a colon.

The only unexplained peculiarity of the observation remaining is Swift's note of "Previous" in the "Date" column. Gary points out that if we take the previous entry in the table (10 Oct 1897), the object would only be a few degrees from the sun and unobservable. So, "Previous" must refer to some other date. If, for example, the object were actually IC 2974 as I had suggested earlier, then it might point to the date for that earlier discovery. However, as IC 2975 is almost certainly not IC 2974, I am going to suggest that this word is a reference to the "previous" observation implied in Swift's note "Saw it twice, failed once." Perhaps he simply copied his own internal note "Previous" from his lost observing logs. This is simply a guess, but I also note that nowhere else in his many lists of new nebulae does Swift use the word "Previous" in the date column. He lists the day in all but a handful of cases, and goes to some effort to make the month and year clear, too. In any event, we don't know the discovery date of this object beyond the year (1897 -- or perhaps 1898 given the uncertainties in the discovery years given elsewhere in the 12th list).

Note, too, that the first paragraph of my previous note -- preserved above -- conflates the descriptions of the two objects. This turns out to be simply wrong. I hope I've got it all right now!

― IC Notes by Harold Corwin

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