M 103

For any telescope

M 103 (NGC 581, Melotte 8, Collinder 14, Raab 4, OCL  326) is an open cluster in Cassiopeia, located within 1o of Delta Cas. An intermediately rich group, M 103 contains between 40 and 50 stars within a 6' circle. The brightest star is the 7th magnitude multiple star system HD 9311 (Struve 131). The stars in this cluster lie about 9000 light years away from us, which is about 10% of the size of the Milky Way's disk.

Perhaps the most interesting thing about this cluster is the appearance of curving star chains radiating outward from the center. The result can be a 3-dimensional illusion of a concave appearance. To me this cluster looks very much like a spider's web, and I think of it as the "Spider's Web" cluster. Also look for a prominent 10th magnitude red giant star on the southeast edge.


The view in a 6" at 135x. North is down and east is to the right.