NGC/IC Project Restoration Effort

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NGC6237

 

Basic Information


Location and Magnitude


Right Ascension: 16:44:7.4
Declination: +70:38:5
Constellation: DRA
Visual Magnitude:

Historic Information


Discoverer: Swift L.
Year of discovery: 1884
Discovery aperture: 16.0

Observational


Summary description: eF, S, E
Sub-type: NF

Corwin's Notes

===== 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 for Swift to have picked up. These are NGC 6232, 6236, and 6248. Swift's RA's for the three are systematically too small by 14 to 31 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 -- NGC 6237 and NGC 6245 -- do not exist on the sky, so I've simply entered them as "Not found" in the table.