Abstract:
We present colour–magnitude diagrams of open clusters, located in the range 112˚< l<
252˚ , manifesting stellar populations in the background of clusters. Some of the populations
are found to be located beyond the Perseus arm and may be the part of the Norma-Cygnus
(outer) arm. The outer arm seems to be continued from l ∼ 120˚ to ∼235˚ . The background
populations follow the downward warp of the Galactic plane around l ∼ 240˚ .
