Harold Corwin

IC 1270 = NGC 6488. Many years ago, for IC 1270 I chose a star at the same declination as Swift left us (+62 14.4, precessed to B1950), and about 10 seconds east of his RA (17 47 20, again precessed to B1950). I'm pretty sure that I did not take into account his description ("eeeF, S, R, bet a * and 3 sts slightly curved; np of [NGC] 6488; eee diff"). Had I done so, I would have almost certainly done what I am doing now -- wondering just what Swift saw that 11th night in June of 1888.

There are certainly no galaxies in the area aside from NGC 6488 -- ironically, discovered by Swift himself nearly two years earlier on 1 Sept 1886 -- so I thought he must have picked up one of the several faint stars here. I chose the obvious one near his position, clearly not taking his description of the field into account. There is just no match with the field, so the star cannot be his object.

So, pondering this problem again in December 2013, I decided to follow up on NGC 6488. I discovered the most interesting description of it in Swift's fourth list (in AN 2752): "pF, pS, E; bet a pair of sts and a trio of sts in form of a semi-circle." This sounds to me like the same galaxy, and the same star field, seen on two different nights. The field matches Swift's first description a bit better, but the second could be made to work without too much stretching.

So, I'm now almost certain that Swift simply rediscovered NGC 6488, and added the note referring to it after he noticed that the positions were fairly close on the sky (see NGC 6497 = NGC 6498 for another similar case). If that is what happened, he almost certainly did not see two galaxies in the field on that second night (11 June 1888) -- he just reobserved NGC 6488 alone and, given his poor positions, assumed two nebulae in the area when he was preparing his 7th list (in AN 2859) for publication.

― IC Notes by Harold Corwin

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