CORRECTIONS TO THE RNGC:7

(Submitted For Publication in the Webb Society Quarterly Journal)

Steve Gottlieb
1020 Ramona Avenue
Albany, CA 94706
USA
e-mail: sgottlieb@telis.org

NGC 347: Marth discovered a group of galaxies NGC 340, 342, 345, 347, 349 and 350 on the same evening in Aug. 1864. His positions compared to the GSC are accurate for all members. The RNGC and DSFG identify N347 = M-01-03-63, a faint anonymous galaxy located 1.5' SW of a 7th magnitude star (BD-7 159 = SAO 129988) and this is the galaxy recorded in my 17.5" observation:

"Extremely faint, very small, round, only visible intermittently with averted, mag 15 star just off SW edge confuses observation and mag 7.2 SAO 129088 1.5'NE severely hampers the view."

Marth's position is 01 01.6 -06 45 (2000) and is nearly coincident with a galaxy at 01 01 35.1 -06 44 01 which is 4' north of the mag 7.5 star. ESGC (Equatorial-Southern Galaxy Catalogue) also identifies this object as N347. Bigourdan observed N347 and commented "I suspect an exceedingly faint object which could be nebulous, and which is situated toward 3 , d = 4', with respect to BD-7 159." In my 17.5", this galaxy was more prominent and appeared:

"Very faint, round, 20" diameter, very weak concentration. Located 4' north of mag 7.5 SAO 129988. A mag 13.5 star lies 2.1' NE."

In addition, Bigourdan catalogued IC 67, IC 68, IC 71 and IC 72 in the immediate vicinity but all appear either to be very faint stars or nonexistent. PGC gives the correct position for N347 but incorrectly equates it with IC 71 and M-01-03-63.

NGC 758: Although the identification of this galaxy discovered by Leavenworth is correct, the RNGC has imprecise coordinates. The GSC position is 01 55 42.1 -03 04 00 (J2000). The RNGC lists this galaxy 0.3 time-minutes further east and 2' south and should be modified to 01 54.4 -03 11 (1975).

NGC 971: Discovered by Lord Rosse in the N978 group. N971 is identified in the RNGC as one of the components of a double system whose other member is N970. I was not able to resolve this system visually and appears quite difficult to achieve based on the appearance on the POSS.

Rosse's observation on 11 October 1850 placed N970 (gamma on the sketch) 119" in PA 21 from N969. At this exact separation and position angle is the small double system mentioned above. But Rosse's N971 (delta on the sketch) is a mag 15.1 star which is 154" northeast of N996 (Rosse placed it at 151" in PA 39 degrees).

The GSC has the following 2000 positions for these objects:

NGC 970:  02 34 11.8  +32 58 38 (double galaxy)
NGC 971:  02 34 16.0  +32 58 47 (mag 15.1 star)

The MCG identifies the double system as N970 which is correct. N971 should be stricken listed as nonexistent in the RNGC as it only applies to a 15th magnitude star.

NGC 998: Marth discovered N997 and N998 in October of 1863 and placed N998 2s of RA following N997 and 1' north. His precessed positions for 2000 are:

Marth 64	02 37 15  +07 19  "F, S"  = N997
Marth 65	02 37 17  +07 20  "vF     = N998

There are three galaxies in the vicinity with the following GSC positions:

U02102	        02 37 14.5 +07 18 23  = M+01-07-016 = Z414-27
M+01-07-015	02 37 16.5 +07 20 09
Z414-028	02 37 20.3 +07 26 23

So, the following identifications appear secure based on Marth's position:

N997 = U02102 = M+01-07-016 = Z414-27 N998 = M+01-07-015

The third object, M+01-07-015, is a small, faint galaxy situated 1.8' NNE of N997 which I observed with my 17.5" and certainly would have been picked up by Marth using Lassell's 48".

Here is where things get interesting regarding N998:

CGCG, UGC (notes) and RNGC all misidentify Z414-028 as N998. UGC lists the correct N998 in the notes for N997 although as an anonymous companion. PGC has the correct galaxy but incorrectly equates M+01-07-015 = Z414-28. These errors probably originated in CGCG.

Two sources have the correct object: MCG identifies M+01-07-015 = N998 as well as Reinmuth (Die Herschel- Nebel, 1926). MCG incorrectly places N998 3s of RA west of N997 but N998 follows N997 by 2s of RA.

NGC 2232: This is a scattered open cluster surrounding 10 Monocerotis (V = 5.0) and the NGC position from William Herschel coincides with this bright star at 06 27 57 -04 45.7 (2000).

The position given in RNGC, Lynga #5, NGC 2000.0 and Sky Catalogue 2000.0 is 06 26.6 -04 45 (2000) and is about 20' too far west (almost the cluster diameter). Brian Skiff suggests a centroid position of 06 28 02 -04 50.8 (2000) based on the GSC star 4793-2505. So, the RNGC position should be modified to 06 26.8 -04 50 (1975)

NGC 2806: Dreyer's notes from 22 March, 1876 state: "A vF * or cS, eF neb p [N2809] (sky bad), forming an equilateral triangle with [2807] and [2809] (susp as neb by d'A, = [N2806])." At this position there is a mag 14.5 star which is listed in the GSC at 09 16 56.7 +20 04 14 (2000). This star forms an equilateral triangle with N2807 and N2809 as stated by Dreyer and lies due west of N2809. Since his descriptions and offsets for other objects in the field are exact, there is no mistaking the identity of N2806 as a single star.

RNGC, MCG (M+03-24-030), DSFG and U2000 misidentify N2806 with an extremely faint companion of N2807 situated just preceding the south edge. This galaxy was highly suspected in my 17.5" although apparently it was not seen by Dreyer! (he did note the sky was bad). This galaxy (M+03-24-030) should not receive a NGC designation. The RNGC should reclassify N2806 as nonexistent with the comment "=*" in the notes column.

NGC 2866: John Herschel's position 09 22 04.4 -51 06 08 (2000) and description "Cluster class VIII. Place of a small compact knot of st" is a dead-on match with a small group of stars. Unfortunately, the RNGC description says "NOCL" and Lynga #5 open cluster catalogue and Sky Catalogue 2000 identify the cluster as Pismis 13. The GSC shows the group very prominently and ESO gives the correct identification although with a question mark.

NGC 3148: Here is an interesting case from John Herschel. h675 was recorded once on sweep 328 and described as follows: "a star 7m has a photosphere 2 or 3' diam. Sky perfectly clear; glass quite clear; windy. Another * of same magnitude viewed presently after has no photosphere."

His description and position (about 30" too far south) applies to mag 6.6 SAO 27566, which is not surrounded by any nebulosity or halo. There are other cases where Herschel recorded glare around brighter stars and this seems to be a similar situation although his description implies he was careful to avoid this.

The Rosse observers at Birr Castle made 4 observations of this object although the single published description from March 1849 simply reads "S * at sp edge of neby" with no mention of the bright star. Reinmuth (Die Herschel-Nebel, 1926) describes N3148 as a *6.5 = BD 51 1585, with no mention of a nearby galaxy.

RNGC and MCG identify N3148 as M+08-19-011, which is located about 4.5' SW of the bright star. This galaxy is given a photographic magnitude of 16 in MCG and is not catalogued in CGCG or RC3. Based on its photographic appearance, it seems very hard to believe that Herschel could have seen this 16th magnitude galaxy in the glare of a bright star or possibly confused it as a "photosphere 2 or 3' diam" surrounding a mag 6.6 star, so the RNGC/MCG identification appears incorrect. Most likely, Herschel was simply confused by scattered light or reflections from the bright star.

NGC 3272: N3272 was discovered by Herman Schultz on 9 Mar 1866. His micrometric position for Nova VI is 10 31 48.1 +28 28 07 (2000). This position is a dead-on match with a close double star on the GSC (mag 12.7/13.7 at 4"). In the notes section of his monograph "Micrometrical Observations of 500 Nebulae" Schultz describes this as "an insignificant object; p h721 [N3277] ab[out] 68s and 160" s; a * 10m f 0s.2 and 135" n."

There is a mag 11 star at GSC position 10 31 48.1 +28 30 22 (J2000) which is exactly 135" north of the double star and the offset with N3277 also matches, so there is no doubt of this identification. On the night this double star was found, Schultz recorded the sky conditions as "Aurora. Images dull." This probably contributed to the close double star appearing nebulous.

RNGC misidentifies N3272 with an anonymous galaxy (not on GSC) at ~10 32 10 +28 29.0 (measured from DSS). This faint galaxy is not listed in CGCG, MCG or RC3. As it is reasonably close to Schultz's position, RNGC took the nearest galaxy around as N3272.

NGC 4055, 4057, 4059: These NGC entries have an uncertain declination ("PD very doubtful") as John Herschel gave only a rough declination of ~32 (1830) for these objects. All three objects were described as "pB" although they are not listed in modern catalogues except RNGC which misidentifies N4057 with an extremely faint galaxy 3.0' west of N4090 and PGC which identifies N4059 with IC 759.

Harold Corwin has suggested that these objects are most likely duplicates entries as follows: N4055 = N4061, N4057 = N4065, N4059 = N4070 (the fourth relatively bright galaxy in the vicinity, N4066 was seen in the same sweep).

Although the RNGC lists N4055 and N4059 as nonexistent, N4057 is certainly misidentified as should be reclassified as nonexistent with the comment "=N4065?" in the notes column.

NGC 4824: Discovered by Bigourdan within Abell 1656 (Coma galaxy cluster). His offsets from his comparison star coincides with a single mag 14-15 star in the GSC at 12 56 36.4 +27 25 57 (J2000).

RNGC misidentifies this number with an anonymous galaxy 6.4' due north of this star at 12 56 34.2 +27 32 20 (J2000) and N4824 is also incorrectly plotted at this position on the U2000. The RNGC type should be listed as 7 (nonexistent) with the notes column reading "=*".

NGC 5785, 5788: Both of these objects were discovered by Swift on 21 Apr 1887. N5788 was described by Swift as the southeast of a pair with N5785 and both were placed following N5783 (the position of N5783 must have been communicated directly to Dreyer as it does not appear in any of Swift's lists). Swift placed N5785 at 14 53 58 +52 07 11 (2000) and N5788 at 14 54 27 +52 05 14 with the NGC positions about 1' further north.

The UGC and CGCG equate N5785 = N5783 at 14 53 28.4 +52 04 37 (2000). Swift's position for N5785 is 30s following N5785 and 3' north so this equivalence is very uncertain although his description "F* nr f" is a reasonable match with the mag 14.5 star at the north edge. RNGC lists N5785 as nonexistent.

The RNGC identifies N5788 = M+09-24-049 = Z273-032 at 14 53 16.9 +52 02 39 (2000). As this position is southwest of N5783, this identification appears unlikely.

Neither of these objects were found by Bigourda and since there are no galaxies at the positions of N5785 and N5788 (which should follow N5783), these numbers are likely nonexistent. The galaxy M+09-24-049 located 2.6' southwest of N5783 would then be an anonymous galaxy and not N5788 as listed in the RNGC. It is possible that N5785 is a duplicate of N5783, although the evidence is not conclusive.

NGC 5867: Discovered by Lord Rosse and observed on two occasions (out of 12) close south of N5866. Described in the 25 April 1851 observation as "alpha [labeled on sketch] is an eeF neb" and on 13 April 1855, "the nova alpha seems to a real neb".

There is an extremely faint galaxy 2' south of N5866, exactly at the relative position shown on the Rosse sketch with respect to the bright galaxy and nearby field stars. Although very small, this object is clearly nonstellar on the Burnhamís photo on N5866 (at the bottom border) and in Hubbleís Atlas of Galaxies. Reinmuth identifies N5867 as a mag 14.5 star 3.8' SSE of N5866, although this star is bright enough to be an easy target for the Birr Castle 72" Leviathan.

The RNGC lists N5867 as nonexistent but the precise position for this galaxy is 15 06 24.3 +55 43 53.6 (J2000).

NGC 7594: This galaxy from Common is member of a small group including ICís 5305, 5306 and 5307 from Kobold and IC 1478 from Bigourdan. There are only four reasonably bright galaxies in the group, so one of these numbers must be a duplicate. The IC positions are very good and imply the following identifications:

GSC positions (2000)    IC id's and positions (2000)
23 18 06.2  +10 17 59   IC 5305 = 23 18 03  +10 17.8
23 18 11.3  +10 14 46   IC 5306 = 23 18 08  +10 14.8
23 18 13.9  +10 17 54   IC 1478 = 23 18 14  +10 19
23 18 22.0  +10 14 08   IC 5307 = 23 18 19  +10 14.0

If you add 3s of RA to Kobold's positions they are exact matches with the GSC.

Now, the remaining object is Common's N7594 which he gave a rough position of 23 18 28 +10 12 (2000). Based on his declination, this would suggest that N7594 = IC 5306 or IC 5307 (the two southern members). In fact, RC3, MCG and RNGC all identify the double system IC 5306 as N7594 (an elongated system 0.7x0.3 roughly E-W), although in the Notes column, RNGC equates this galaxy with IC 5307. CGCG also lists this galaxy, but as IC 5306. It is important to note that Common's positions (particularly declination) are often 10' to 15' off.

Common's original description in Copernicus (Dreyer cut it down) reads: "F, R, f 3 stars in a line 90 degrees pointing to another fainter nebula s(outh)." Comparing this description to the POSS it is clear that Common's N7594 = Bigourdan's IC 1478.

Preceding IC 1478 by just under 2' is a perfect collinear trio consisting of two mag 14 GSC stars and IC 5305 which Common may have mistaken for stellar. Furthermore, continuing this line to the south you quickly run smack into IC 5306 matching his description. This pins down the identification of N7594 = IC 1478 = U12485 = M+02-59-023. The RNGC position should be changed to 23h 17.0m 10 10' (1975) and the data changed to U12485