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NGC 1649 (3,068 of 18,816)

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NGC 1649

NGC 1649, NGC 1652, ESO 55-31, ESO 55-32, LW 14, SL 10, h 2660, GC 897

RA: 04h 38m 22.9s
Dec: −68° 40′ 18″

Con: Dorado
Ch: MSA:486, U2:444, SA:24

Ref: NGC/IC, SIMBAD

(reference key)

Type: open cluster

Mag: B=12.5, V=12.9

Size: 1.5′
PA: ?

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

NGC 1649 = NGC 1652. JH has only one observation of NGC 1649 in Sweep 523 that puts it about 9 arcmin south and 6 seconds preceding NGC 1652 (his original data for N1649 are 04 38 43.3, -69 08 37 for 1830). This is only a few arcsec from the star SAO 249073, but JH makes no mention of a nearby bright star in his observation.

NGC 1652 is an LMC cluster which JH observed on three nights (Sweeps 508, 653, and 759) with fairly accordant positions (the unweighted mean is 04 38 49.2, -68 59 56). He did not record N1652 in the sweep in which he found N1649; he has it only in the three other sweeps of the area.

Also interesting are his descriptions: they are virtually identical in sweeps 523 and 759. He writes `F, R, gbM, 30",' and `F, R, gbM, 35",' respectively. The descriptions in sweeps 508 and 653 make the cluster `vF, S, R, gbM, 12" ' and `vF, S, R'.

Since the difference in declination is close to 10 arcmin (a digit error that JH and others made several times), and the RA's are not very much different -- many other CGH observations also show RA differences of six seconds or more of time, especially as far south as the LMC -- I think that the two NGC numbers refer to the same object. Hodge and Wright came to the same conclusion in the LMC Atlas, but are rather cautious and say, "Possibly NGC 1652. Declination off by 9'."

However, just eight arcmin south of NGC 1652 is a faint LMC cluster (ESO 055-SC031 = KMHK 022) that Lauberts, in ESO-B, suggested might be NGC 1649, though with two question marks and a note commenting on the declination difference. He also has N1649 = N1652 with one less question mark. KMHK (Konzitas et al, A&AS 84, 527, 1990) do not use the NGC number on the cluster, and apparently did not notice the ESO-B entry. Bica et al (AJ 117, 238, 1999), however, use N1649 for the cluster, and also note the ESO entry.

Jenni Kay has also picked up the faint cluster with her large reflector, so it is not impossible that JH saw it while sweeping. In an email to Jenni and to Mati Morel (who alerted me to Jenni's observation) I wondered, though, if the star might hinder JH's ability to see the very faint cluster. It certainly did not get in Jenni's way!

In response, Mati listed eight cases where JH found objects near bright stars (V < 9.5) in the LMC. JH mentions the star (or stars) in only four of his descriptions, so the presence of the star alone would probably not be an obstacle to his having seen the cluster, assuming that it (the cluster) is bright and large enough to have attracted his notice during a sweep.

So, I do have a bit of doubt about the identity of NGC 1649 -- but not much.

Historical observations

John Herschel

John Herschel observed it only once, on 23 December 1834, when he recorded it as "faint; round; gradually brighter in the middle; 30 arcsec across."

Published comments

Lindsay, E.M. (1964)

Lindsay, E. M. (1964) Some NGC objects in the Large Magellanic Cloud", IAJ, 6, 286-289. [1964IrAJ....6..286L]

Not found. Centred on CPD -69°284. Possibly the faint cluster S/L 8, 13' south.

Lortet, M.-C. (1986)

Lortet, M.-C. (1986) Nomenclature for objects in the Magellanic clouds. Astrophys.J.Suppl.Ser., 64(2), 205-390.

Notes that Morel lists NGC 1649 as nonexistent.

Sulentic & Tifft (1973)

(Sulentic and Tifft 1973) notes that this is a nonexistent object. Their coded description reads =1652 HODGE.

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