King 21

Number of stars per data source

	Reference  128 :   22 stars
	Reference  326 :    3 stars
	Reference  385 :   23 stars

References

 128
Lasker B.M., Russel J.N., Jenkner H., Sturch C.R., McLean B.J., Shara M.M.
(1990) Astron. J. 99, 2019
The HST guide star catalogue, version 1.0
1990AJ.....99.2019L
 326
Hog E., Fabricius C., Makarov V.V., Urban S., Corbin T., Wycoff G., Bastian U., Schwekendiek P., Wicenec A.
(2000) Astron. Astrophys. 357, L27
The Tycho-2 Catalogue
2000A&A...355L..27H
 385
Skrutskie M.F., Cutri .M., Weinberg M.D., Schneider S., Carpenter J.M., et al.
(2006) Astron. J. 131, 1163
The Two Micron All Sky Survey (2MASS)
2006AJ....131.1163S