  Photoelectric, photographic, and CCD UBV photometry, spectroscopic
observations, and star counts are presented for the open cluster Berkeley 58 to
examine a possible association with the 4.37d Cepheid CG Cas. The cluster is
difficult to separate from the early-type stars belonging to the Perseus spiral
arm, in which it is located, but has reasonably well-defined parameters: an
evolutionary age of ~10^8 years, a mean reddening of E(B-V)_(B0)=0.70+-0.03
s.e., and a distance of 3.03+-0.17 kpc (V_0-M_V=12.40+-0.12 s.d.). CG Cas is a
likely cluster coronal member on the basis of radial velocity, and its period
increase of +0.170+-0.014 s yr^(-1) and large light amplitude describe a
Cepheid in the third crossing of the instability strip lying slightly blueward
of strip centre. Its inferred reddening and luminosity are E(B-V)=0.64+-0.02
s.e. and <M_V> =-3.06+-0.12. A possible K supergiant may also be a cluster
member.
