  We have studied the poor southern cluster of galaxies S639. Based on new
Stromgren photometry of stars in the direction of the cluster we confirm that
the galactic extinction affecting the cluster is large. We find the extinction
in Johnson B to be A_B = 0.75+-0.03. We have obtained new photometry in Gunn r
for E and S0 galaxies in the cluster. If the Fundamental Plane is used for
determination of the relative distance and the peculiar velocity of the cluster
we find a distance, in velocity units, of 5706+-350 km/s, and a substantial
peculiar velocity, 839+-350 km/s. However, the colors and the absorption line
indices of the E and S0 galaxies indicate that the stellar populations in these
galaxies are different from those in similar galaxies in the two rich clusters
Coma and HydraI. This difference may severely affect the distance determination
and the derived peculiar velocity. The data are consistent with a
non-significant peculiar velocity for S639 and the galaxies in the cluster
being on average 0.2 dex younger than similar galaxies in Coma and HydraI. The
results for S639 caution that some large peculiar velocities may be spurious
and caused by unusual stellar populations.
