NGC 6237

History and Accurate Positions for the NGC/IC Objects (Corwin 2004)

NGC 6237 and NGC 6245 may be duplicate observations of NGC 6232 and NGC 6236, respectively. Or they may be stars. Or, they may simply be "not found."

Whatever the case, these are two of a group of four nebulae that Lewis Swift found on the night of 28 June 1884; the other two are NGC 6232 and NGC 6236. Over a year later, on 11 August 1885, Swift found another nebula, NGC 6248, about half a degree south of his group. There were no other observations before Dreyer compiled the NGC, so he included all five.

Looking at the area on the Sky Survey prints, we now see only three galaxies here that are bright enough that Swift could have seen them. These are NGC 6232, 6236, and 6248. Swift's RA's for the three are systematically too small by 20 to 25 seconds of time, but his declinations are very good. Looking at his positions for the missing two objects shows that the declination of NGC 6237 is close to that of NGC 6232, and that for NGC 6245 is similarly close to that for NGC 6236. In addition, his RA's for the two missing objects each have roughly the same offset from the RA's for the same two galaxies (32 seconds in the first case, 48 seconds in the other).

So, I wonder if NGC 6237 = NGC 6232 and NGC 6245 = NGC 6236 -- in spite of the fact that Swift found all of the objects on the same night, and explicitly noted "1st of 4," "2nd of 4," etc, in the descriptions of all four objects. Keep in mind his method of finding positions: centering the object in the eyepiece, and reading the setting circles. Did he perhaps bump the telescope or setting circles inadvertantly after reading positions for the first two objects?

Still, he used a very large field eyepiece, so it may be that he mistook stars near the galaxies as other nebulae. Or, he may have seen reflections of stars out of the field and mistook them as nebulae. Or, his eyes may have played tricks on him if he was tired. I favor the jarred telescope/setting circle hypothesis, but would not bet even a nickel on its being right.

Whatever happened, the two objects do not exist, so I've simply entered them as "Not found" in the table.

Published comments

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a galaxy. Their coded description reads EL,IRR,BM,DIF,KNY.