Basel 11b -- Open Cluster in Orion
My Favorite Basel Open Cluster
The Basel Open Cluster Catalogue is a list of twenty Open Clusters produced at the Basel
Astronomical Institute (one of Switzerland¹s leading centers of astronomy) during the 1960s.
Most of the clusters are small and unimpressive in amateur telescopes. My favorite, of the
Basel Open Cluster List, is Basel 11b in the far northeastern corner of Orion. Basel 11b is
really small (3.0 arcminutes) but stands out in the eyepiece at modest powers with little effort.
In the 155mm refractor from my yard, I can only detect about 5 or 6 stars in the cluster proper,
while the rest of the 60+ stars form a background mist in which these stars are embedded.
Part of the charm of this tiny cluster is that it sits in a attractive field of stars that fills the
eyepiece and accents the view of Basel 11b.