NGC/IC Project Restoration Efforts

===== NGC 3010. There are three galaxies here that are occasionally numbered "NGC 3010A", "NGC 3010B", and "NGC 3010C" (though I have deleted these suffixes from the position table; they made the table very difficult to read. For the record, "N3010A" is the middle galaxy, "N3010B" is the southwestern, and "N3010C" is the northeastern). JH's position is far enough off that it does not help, at least in an absolute sense, in identifying his object. However, his position for NGC 3009, seen in the same sweep and called "The first of 2" -- NGC 3010 is "The second of 2" -- is also off: the RA correction is +17 seconds, and the Dec correction is -1.6 arcmin for NGC 3009 if we take the larger and brighter (though lower surface brightness) spiral five arcminutes southwest of the triple as the first of the pair that JH saw. Applying these corrections to JH's position for NGC 3010 gives 09 50 17, +44 19.2 (J2000), still about 20 seconds of time west of the triple, though the declination has fallen in line. The problem with this is that the position for NGC 3009 is far enough off to throw its identification in doubt, too. So, how about JH's descriptions? As published, they read for NGC 3010: "F, psbM, r, stars seen. The second of 2." The "r, stars seen" could refer to the nuclei of the three galaxies. (But there are also a few faint stars to the north that JH might have picked up.) For NGC 3009, his published description reads "Not vF, R, bM, r. The first of 2." These -- setting aside "The first/second of 2" -- unfortunately are generic enough that they could fit any of the four galaxies. Finally, it is also possible that his observations here actually refer to two of the three galaxies of the triple. JH's RAs support this in that he has only six seconds of time between his two objects, the same difference as between the western and eastern galaxies of the triple. His declination difference is 1.5 arcmin, while the declination difference between the eastern and western galaxies of the triple is 1.0 arcmin, certainly within his nominal error bars. While my own inclination would be to select the two brightest galaxies of the triple as JH's pair, I don't think that he has left us quite enough to go on to select any two of the four galaxies as the ones his observations refer to. Unfortunately, this means that I am going to leave the "traditional" identifications in place, but with question marks on them. Not very edifying, I know, but there it is. ----- There things stood until May 2015: Courtney Seligman wrote about these two objects, saying essentially that he was not happy with the traditional identifications (this makes at least two of us!). This led me to check JH's sweep in the Herschel Archive. He has a note attached to his 17 March 1828 observation of the two nebulae: "Something unaccountable in the taking of the RA's here John[??] must surely mean[??] +12- -43 in the 2nd obs." The actual RA observation for the 2nd object reads "-12 -43", where the first number is found in the column where the minutes of RA on the clock is usually written. The "-43" is perhaps the chronometer correction (which JH calls the "beat"), though the minus sign is stronger than usual, and is in the column usually reserved for the seconds of time on the clock. I can see why JH was puzzled when he came to reduce these observations! My own guess is that the "-12" is seconds of time, and the "-43" is simply a repeat of the "beat" for the first object. JH's descriptions from the sweep are "a pair" with a bracket around that, and a simple diagram showing the two objects at roughly a 30 degree orientation with respect to one another, assuming horizontal on the page is east-west. If south is at the top in this diagram, then the brighter nebula is to the southwest. The next object in the sweep is the double star at 10 01 25.4, +44 58 09 [J2000]; its diagram has the same orientation as the diagram of the nebulae. On the sky, the orientation is southwest-northeast just as the nebulae are oriented. The description for the first object reads "not vF, bM, R, r, gbM". There are indeed two "bM" notations, probably to distinguish it from the second object, which is described as "F, resolvable, stars seen, psbM." Looking at the observation of the first nebula in the sweep, I see that it reads "9 39 50 -43" and is perhaps referred to the second wire (though the "2" is very close to being a flat line; perhaps it is not the second wire, but the first, the trailing edge of the field, or even a "null". I see other "2"s in these sweeps written the same way, but this is most extreme example I've noticed). The second nebula is definitely referred to the second wire; if so, the two RAs ought to be directly comparable. The NPD index for the first is "2 39 30", and for the second "1 1/2' north". For the star "15 Leo Min" -- observed just before the two galaxies -- JH has "9 37 15 -14" for the clock and chronometer beat, wire "1", and "0 56 55" for the NPD. All this implies offsets between the star and the first galaxy of +1m 27s and -1d 42' 35" which gives a position of 09 49 51, +44 18.6 (J2000), in close agreement with JH's own published position 09 49 54, +44 19.3 (precessed to J2000). If, however, we assume that the wire was mistaken and that wire 1 was the actual wire that JH used for the transit, then the RA offset becomes +2m 13s, and the J2000 position is 09 50 36, +44 18.6, close to the first galaxy in the triplet, MCG +07-20-065. This would imply that JH's second nebula is within 12 seconds of this one and 1.5 arcminutes north. This suggests that MCG +07-20-067, the northeastern galaxy in the triplet, is JH's second nebula. This, however, is the faintest of the three (see Steve Gottlieb's observations below). On the right-hand page where JH normally gives the reduced positions, he has another note, "Must be re-reduced". Under that are the two positions for the objects that became NGC 3009 and NGC 3010: "9 39 1:, 44 53 50" and "9 39 7:, 44 52 20" (RA and NPD 1830 for both). Just to the right of those is another column headed "Re reduced [sic] See Red. Book". The positions in this column read "9 39 6.4, 44 53 34" and "9 39 12.4::, 44 52 0:". These latter positions are those that JH published in his 1833 catalogue, but the published positions do NOT carry the uncertainty symbols. Putting all this together, I am going to suggest that JH observed two of the three galaxies that we in the past called "NGC 3010", perhaps the southwestern and the northeastern. These are separated only by 6 seconds in RA and a minute of arc, less than JH's estimates (assuming that the "-12" for the second object is indeed a difference in RA of 12 seconds), so I am obviously not going to insist that this is correct. His descriptions are puzzling, too, but as I mentioned above, they might be understood if he glimpsed the third galaxy and some of the nearby stars. [Wolfgang suggests that the "-12" is a chronometer difference; if so, the six second difference in RA matches JH's measurement given the two beats per second of the chronometer. I'll have more to say about this below.] What about the galaxy traditionally called "NGC 3009"? This is bracketed by JH's RAs from the two different wires with the declination being about an arcminute south. However, a 12 second and 1.5 arcminute difference to the second galaxy from this one works pretty well in declination, but not in RA. And while the western-most galaxy of the four, MCG +07-20-062, is larger, it has a lower surface brightness. Given the similarity of JH's descriptions for his two objects, I'm a little less happy with the idea that he saw this one and just one of the other three. But again, see Steve Gottlieb's notes that I've quoted below. So, I offer two of the galaxies in the northeastern triplet as a reasonable -- though obviously questionable -- interpretation based on the information in JH's sweep. Finally, Courtney's discussion has led me to look into other observations of the galaxies here. LdR reports two observations of the area. The first is from 1 March 1854, presumably by R.J. Mitchell who writes "One pB; 6'f and a little north are two others vF, about 3' apart pf; several others round about." (We'll come back to the "several others" in the addendum below.) On 1 April 1878, Dreyer at the eyepiece has "1933 [N3009] and 1935 [N3010] seen for a few minutes ..., the f one is smaller and in a rectangular [triangle] of 3 sts." These are pretty clear descriptions of the two brightest objects, the ones that we have taken as N3009 and N3010. On 17 Mar 1895, Bigourdan has micrometric observations of the two brightest galaxies in the area, MCG +07-20-062 and -065. In his description of "NGC 3010", he mentions "A star, even fainter than this object, is at P = 20deg, d = 0.'7." This "star" is actually the middle of the three galaxies. In June of 1991, Steve Gottlieb observed the objects with his 13-inch reflector. His notes: UGC 5264 = MCG +07-20-062: "F, S, R, even Surf Br" MCG +07-20-065: "vF, S, R" MCG +07-20-066: "vF, S, R" MCG +07-20-067: logged as a mag 15.5 "star". [O]f the 4 objects MCG +07-20-067 was the least obvious to me -- in fact, I recorded it as a dim star in my notes. Although MCG +07-20-062 has a lower surface brightness than -065 or -066, I think it was at least as obvious due to its larger size. This suggests that MCG +07-20-067 was less likely to have been seen by JH. So, we need to take all this into account, too. Bigourdan saw three galaxies here, but took one to be a star, while Steve picked up all four, but like Bigourdan, saw one as a star. In the end, I've arrived at the really messy identification list shown in the position table. Summarizing, here is how I've broken it all down: NGC Alternate RA (J2000) Dec Obs Notes IDs 3009 09 49 54 +44 19.3 oJH As published. 3009 09 50 36 +44 18.6 oJH Assumes wire 1, not wire 2. 3009:: +07-20-065 09 50 33.2 +44 18 52 c2MSP = NGC 3010sw = NGC 3010B 3009? +07-20-062 09 50 11.1 +44 17 42 cSDSS 3010 09 50 00 +44 20.8 oJH As published. 3010 09 50 48 +44 20.1 oJH Offset from N3009, wire 1. 3010:: +07-20-067 09 50 39.4 +44 19 52 c2MSP = NGC 3010ne = NGC 3010C 3010? +07-20-066 09 50 34.6 +44 19 24 c2MSP = NGC 3010m = NGC 3010A There are still other ways to interpret JH's observations (why, for example, did he make the RA difference just six seconds when the log book has "12"? Did he perhaps take that as a difference in the chronometer "beat" rather than as difference in seconds of time? Wolfgang, as I've said, agrees with this interpretation), so this is not the final word here. At least we know that JH saw two of the four galaxies here -- but which two, we just aren't sure. As before, not very edifying, but the observations just don't pin JH's objects down any better than this. ----- Another note in September 2015: I had an email from Wolfgang (mentioned above) that suggests this sequence of events that might account for JH's records here: 1) JH saw the first nebula -- call it "N1" for brevity -- nearly in the center of his field when the clock read 09 39 50. It had already passed wire 1, and took another 43 chronometer beats (= 21.5 seconds) to reach wire 2. 2) Another 12 beats later (6 seconds), the second nebula crossed wire 2 1.5 arcminutes north of N1. So, Wolfgang's interpretation is that JH's strange notation "-12 -43" means that N2 follows N1 by six seconds, and that N1 was in view for 21.5 seconds before it crossed the second wire. This is reasonable given that the field of view is just over 90 seconds of time wide at this declination, and that the separation of wires 1 and 2 is 45.3 seconds. This leads Wolfgang to say "The short distance N1-N2 speaks against the identification [of] NGC 3009/10." In other words, UGC 5264 = MCG +07-20-062 is NOT NGC 3009. Wolfgang goes on "So we must choose two of the components of the MCG triple (7-20-65, -66, -67). [But Steve Gottlieb has shown that] only the first two [of these] are bright enough -- but they are much closer [just 1.5 seconds] than JH's value." Wolfgang goes on to ask about the issue of JH's description of N2: "resolvable, stars seen". "What are the 'resolvable stars'? Perhaps JH has seen [MCG +07-20-0]65 as N1 and 66/67 plus the scattered stars around as N2. But this is a matter of 15th magnitude!" Wolfgang is right -- these would have been right at the limit of JH's telescope. Yet JH's description of N2's brightness is just "F", not "eF" or even "vF". Wolfgang ends by saying "But facing JH's possible error, N1 = ... NGC 3009 = UGC 5264 and N2 = ... NGC 3010 = [MCG +07-20-0]65 (or 66) could indeed be the correct identification!" ----- And a curious addendum: Looking at the GC, we find that JH includes not just his two nebulae, but has two other entries, GC 1936/37, which he credits to LdR, describing them only as "Several near", and giving a single position for the two "9 41 +-", "45 0 +-" (1860, NPD). Coincidentally, there are only two galaxies in the area aside from the two that JH observed. It is quite tempting to assign these two GC numbers to the two spare galaxies. If we do this, assuming that my double-coloned identifications are "correct", the two left-over objects are MCG +07-20-062 and MCG +07-20-066. (However, they could well be two others!) See the "notngc" files for a bit more on this.

NGC/IC Project Restoration Effort

NGC3010

Basic Information

Location and Magnitude

Historic Information

Observational

Corwin's Notes

Steve's Notes