Messier 47

Discovered before 1654 by Giovanni Batista Hodierna.
Independently rediscovered by Charles Messier on February 19, 1771, but missed.
Independently rediscovered by William Herschel on February 4, 1785.

Messier: M47.

February 19, 1771. 47. "Cluster of stars, little distant from the preceding; the stars are greater [brighter]; the middle of the cluster was compared with the same star, 2 Navis. The cluster contains no nebulosity."

(At the position recorded by Messier, which also found its way into John Herschel's GC as GC 1594 and, consequently, into Dreyer's NGC as NGC 2478, no cluster is found, so that this object was missed, until Oswald Thomas identified it correctly but perhaps by chance in 1934 as Herschel's cluster H VIII.38 (NGC 2422), and T.F. Morris, in 1959, realised that Messier had done a simple sign error in RA difference when reducing the positional data.)

Hodierna: Ha IV.1.

Caroline Herschel

Observed it on February 26, 1783, despite it was later found a "missing" Messier Object. Also observed M41 that night.
Also observed M47 on March 4, 1783, the night she took M46 for a new object (perhaps because of Messier's wrong position for M47).

William Herschel: H VIII.38.

VIII.38. Feb. 4, 1785.
A Cl. of p. com. L. and S. st. R. above 15' d.
A cluster of pretty compressed large [bright] and small [faint] stars. Round. Above [more than] 15' diameter.

John Herschel (1833): h 459.

h 459 = H VII.38 [actually H VIII.38].
Sweep 111 (December 16, 1827)
RA 7h 28m 46.4s, NPD 104d 6' 28" (1830.0) [Right Ascension and North Polar Distance]
The chief * of a L, p rich, straggl cl. It is double.
The chief star of a large, pretty rich, straggling cluster. It [the star] is double.

Smyth: CCXCVI [296]. H. VIII.38 [M47].

CCXCVI. 38 H. VIII. Argo Navis [now Puppis].
AR 7h 29m 12s, Dec N 14d 08'.3
Mean Epoch of Observation: 1834.21 [March 1834]
Position 308d.8 (w 8), Distance 8".0 (w 4)
A double star in a loose cluster of the Milky Way, over the Argo's stern; and one of those seized by Bode to make his Officina Typographica. A 7 1/2 [mag], and B 8, both bright bluish white. Its inhabit a very splendid field of large and small stars, disposed somewhat in lozengeshape, and preceded by a 7th magnitude [star] with a companion about 20" nf [north following, NE] [of] it. The cluster was not registered till 1785 [actually it was seen by Messier but wrongly positioned], but the double star is 63 H. II., the former measures of which are:

      W. Herschel  Pos. 300d 12'   Dist 6".50 +/-   Ep. 1782.78
      South             303d 20'        7".44           1825.02
      Struve            304d 44'        7".46           1831.44
  

To fish this object up, run a line about 12deg east-by-north from Sirius and intersect it by another from Pollux through Procyon, and continued 20deg lower down. It is in a very rich vicinity.

John Herschel (1847): h 3088.

h 3088 = H VIII.38 = h.459.
Sweep 757 (December 11, 1836)
RA 7h 28m 49.6s, NPD 104d 6' 50" (1830.0)
A very L, pretty rich, splendid cluster, which more than fills the field. Place of the chief * a fine double star. [N.B. -- PD by obs 103d, bur this is a mistake. The cluster is VIII.38, and not VII.38, as misprinted in h.459.

John Herschel, General Catalogue: GC 1551.

GC 1551 = h 459 = h 3088 = H VIII.38.
RA 7h 30m 10.8s, NPD 104d 10' 31.8" (1860.0) [Right Ascension and North Polar Distance]
Cl; B; vL; pRi; st L & S. 4 observations by W. & J. Herschel.
Cluster; bright; very large; pretty rich; large and small [bright and faint] stars.

GC 1594 [erroneous M47 position; apparently assigned to Messier's position by John Herschel]
GC 1594 = M47.
RA 7h 48m 20.5s, NPD 105d 3' 19.3" (1860.0) [Right Ascension and North Polar Distance]
Place from Wollaston's Cat[alog]. 0 observations by W. & J. Herschel.
Remark: Auwers assigns R.A. greater by 4m. The cluster has not since been observed. It is probably a very loose and poor one.

Dreyer: NGC 2422.

NGC 2422 = GC 1551 = h 459 = h 3088 = H VIII.38.
RA 7h 30m 11s, NPD 104d 10.5' (1860.0) [Right Ascension and North Polar Distance]
Cl, B, vL, pRi, st L and S; = M47
Cluster, bright, very large, pretty rich, large and small [bright and faint] stars.

NGC 2478 [erroneous M47 position]
RA 7h 48m 20s, NPD 105d 3.3' (1860.0)
NGC 2478 = GC 1594; M 47.
Cluster.
Remark: 2478. M 47. Auwers assigns a R.A. greater by 4m (clerical error, see V.J.S., Vol. I. p. 183)

T.F. Morris (1959)

[Identified M47 with NGC 2422 according to Owen Gingerich (1960) and others]

Owen Gingerich (1960)

[Sky & Telescope, Vo. 20, No. 4 (October 1960), p. 196]
More explicit reasons for this identification [of M47 with NGC 2422] were given independently in 1959 by T.F. Morris, a member of the Messier Club of the Royal Astronomical Society of Canada's Montreal Centre. Dr. Morris suggested that an error in signs in the difference between M47 and the comparison star could account for the position.
Messier determined the declination of a nebula or cluster by measuring the difference between the object and a comparison star of known declination. The right ascension could be found by recording the times at which the object and the star drifted across a central wire in his telescope's field; the time interval gives the difference in right ascension. The differences between Messier's 1770 [actually 1771] position for M47 and his stated comparison star, 2 Navis (now 2 Puppis), if applied with opposite signs, leads to NGC 2422. Clearly, Messier made a mistake in computation!