NGC/IC Project Restoration Effort

===== NGC 6847 may be the star cloud and HII region roughly a degree north and 45 seconds west of WH's single position. Earlier I had this just 30 seconds west. That, however, assumes WH's object was a cluster -- but see his description, given below, where this is clearly noted as a "nebulous" object. This identification was first suggested by Wilhelm Tempel in 1871 in a paper about his discovery of a comet at the Brera Observatory in Milan (my thanks to Wolfgang Steinicke for sending a note about this). There is certainly nothing obvious near WH's place, and Tempel's objects could be the ones he saw. They are immersed in a fairly large star cloud in the Milky Way, which might have led to his comments about the surrounding area. His full description, given in the sweep and repeated by Dreyer in the Collected Papers of 1912, reads, "A resolvable nebulous patch; there are great numbers of them in this neighborhood like forming nebulae; but this is the strongest of them." Another possibility is raised by Dreyer's note in the NGC, "Not noticed by d'A, who has 2 observations of GC 5947 = m 403 [= NGC 6842, a planetary]." Is N6842 the object that WH saw? It is just 2 minutes of time preceding and 3 arcmin south of his position. There may be enough stars around the nebula to lead to WH's description, so this may be a candidate. Checking the sweep, I find no problems with the reduction, or with the adopted position of 12 Cygni, the comparison star. To make Tempel's objects work, WH's offsets from 12 Cygni need to be at least 17m 06s east and 7 arcminutes north. These would translate to a clock reading of 19 44.2 to 19 44.4 instead of 19 44.9, and an index reading of exactly "0" rather than 1 deg 0 arcmin. These are certainly possible errors, but I do not like having to suggest two errors in a single observation; in general, one error is the expectation unless a comparison star is misidentified. I also checked the sweep for other objects referred to 12 Cygni. The object immediately preceding NGC 6847 is NGC 6834 for which WH's RA is 25 seconds too large, though the Dec/NPD is only 4.3 arcminutes too large. The near half- minute error in this cluster's position suggests that a similar error in the RA of NGC 6847 is due to some systematic problem rather than an accident of observation or transcription. This leaves the 1 degree error in the index reading as perhaps the only "blunder" here, if Tempel's suggestion is, in fact, the correct explanation. Two other possibilities are nearby on the POSS prints. First is a clump of stars about 20 arcmin north of WH's position. The second is another clump about 55 arcmin south. Neither of these, however, has "great numbers" of similar clumps nearby. Dreyer notes that Bigourdan found no nebulosity at WH's place, though he searched the area four times. His one micrometric observation (I haven't reduced it) probably points at a double or multiple star. There are many of them around. Finally, using the POSS1 overlays, I thought that this might be identical to "NGC 6846" (which see). However, the overlay copies RNGC's 2 degree error in the declination for N6846 so that it lands on top of the cluster and HII region I noted at the beginning of this story. N6846 is not these objects, though as I said, N6847 might just be. All in all, I am not quite as convinced as I was earlier that Tempel has turned up the correct object. After all, WH included this as a nebula in his catalogue, not as a star cluster, which is what most of the objects in the area would look like at the eyepiece. Perhaps that is what is needed here.