Berkeley 21

Number of stars per data source

	Reference   88 :  769 stars
	Reference  191 : 1138 stars

References

 88

Phelps R.L., Janes K.A., Montgomery K.A.

(1994) Astron. J. 107, 1079

Development of the galactic disk: a search for the oldest open clusters

1994AJ....107.1079P

 191

Tosi M., Pulone L., Marconi G., Bragaglia A.

(1998) Mon. Not. R. Astron. Soc. 299, 834

Old open clusters: the interesting case of Berkeley 21

1998MNRAS.299..834T