Messier 103

Discovered in March or April 1781 by Pierre Méchain.

Messier: M103.

[March/April 1781]. 103.
(Méchain) Cluster of stars between Epsilon & Delta of the leg of Cassiopeia.

(Handwritten position added by Messier in his personal copy: 1h 20m, +61.)

William Herschel:

[Unpublished Observations of Messier's Nebulae and Clusters. Scientific Papers, Vol. 2, p. 660]
1783, Aug. 8. 14 or 16 pL. [pretty large (bright)] stars with a great many eS. [extremely small (faint)] ones. Two of the large [bright] ones are double, one of the 1st the other of the 2nd class. (*) The compound eye glass shews a few more that may be taken into the cluster so as to make them about 20. I exclude a good many straggling ones, otherwise there would be no knowing where to stop.
[(*) Dreyer's note: Neither was cataloged by H. [W. Herschel]. One is Struve 131.]

John Herschel (1833): h 126.

h 126 = Struve 131.
Sweep 213 (September 29, 1829)
RA 1h 21m 58.9m, NPD 30d 11' 18" (1830.0) [Right Ascension and North Polar Distance]
A fine cl; R; rich; rather coarse; 6 or 8' diam; stars 10 ... 11m. One of Struve's "averci".
A fine cluster; round; rich; rather coarse; 6 or 8' diameter; stars of 10th and 11th magnitude. One of Struve's "averci".

Sweep 219 (October 27, 1829)
RA 1h 21m 65.7m, NPD 30d 11' 42" (1830.0)
The chief * in a cl VI or VII class 8' diam, which has one v red * near the middle; stars 9 ... 12m.
The chief star in a cluster of [W. Herschel's] class VI or VII of 8' diameter, which has one very red star near the middle; stars between 9th and 12th magnitude.

Smyth: LV [55]. M103

LV. 103 M. Cassiopeiae.
AR 1h 22m 41s, Dec N 59d 51'.6
Mean Epoch of the Observation: 1832.66 [August 1837]
"A neat double star in a cluster, on Cassiopeia's knee, about a degree to nf of Delta. A 7 [th mag], straw coloured; B 9, dusky blue. This is a fan-shaped group, diverging from a sharp star in the nf quadrant. The cluster is brilliant from the splash of a score of its largest members, the four principle ones of which are from the 7th to the 9th magnitude; and under the largest, in the sf, is a red star of the 8th magnitude, which must be that mentioned by JH [John Herschel], No. 126 of his Catalogue of 1833.
My attention was first drawn to this object, by seeing it among Stuve's acervi; but I soon found that it was also the 103 which Messier describes so vaguely, as being between Delta and Epsilon Cassiopeiae, whereas it is pretty close to Delta, on the Lady's knee."

John Herschel, General Catalogue: GC 341.

GC 341 = h 126 = Struve 131 = M103.
RA 1h 23m 59.8s, NPD 30d 2' 9.3" (1860.0) [Right Ascension and North Polar Distance]
Cl; B; R; Ri; pL; st 10...11. 5 observations by W. & J. Herschel.
Cluster; bright; round; rich; pretty large; stars of 10th and 11th magnitude.

Dreyer: NGC 581.

NGC 581 = GC 341 = h 126; M 103, Struve 131.
RA 1h 24m 0s, NPD 30d 1.5' (1860.0) [Right Ascension and North Polar Distance]
Cl, pL, B, R, Ri, st 10...11; = M103
Cluster, pretty large, bright, round, rich, stars of 10th and 11th magnitude.