NGC 6401 is a globular cluster in the constellation Ophiuchus. William Herschel discovered this star cluster in 1784 with his 47 cm telescope, but mistakenly believed it to be a bright nebula. Later his son, John Herschel, was to make the same error because the technology of the day was insufficient to allow the individual stars to be resolved visually.

NGC 6401
The NASA/ESA Hubble Space Telescope has used its powerful optics to separate the globular cluster NGC 6401 into its constituent stars. What was once only visible as a ghostly mist in the eyepieces of astronomical instruments has been transformed into a stellar landscape.
Observation data (J2000 epoch)
Constellation	Ophiuchus
Right ascension	17h 38m 36.93s
Declination	−23° 54′ 31.5″
Distance	24.450
Apparent magnitude (V)	7.40
Apparent dimensions (V)	4.8'
Physical characteristics
Other designations	ESO 520-SC011, GCL 73, H I-44, h 1982, h 3697, GC 4314
See also: Globular cluster, List of globular clusters