We report optical imaging and spectroscopy of 41 galaxies in a 22 arcmin
square region surrounding Cygnus A. The results show that there is an extensive
rich cluster associated with Cygnus A of Abell richness at least 1 and possibly
as high as 4. The velocity histogram has two peaks, one centered on Cygnus A,
and a more significant peak redshifted by about 2060 km/s from the velocity of
Cygnus A. The dynamical centroid of the spatial distribution is also shifted
somewhat to the NW. However, statistical tests show only weak evidence that
there are two distinct clusters. The entire system has a velocity dispersion of
1581 km/s which is slightly larger than other, well studied, examples of rich
clusters.Comment: 11 pages LaTeX, 1 table, 3 postscript figures. Accepted for
publication in Ap.J. Letter