The very reddened open clusters Pismis 23 (Lyngå 10) and Stephenson 2

Pismis 23 and Stephenson 2 are two very reddened open clusters, projected close to the Galactic plane. We present VI and JH photometry for Pismis 23 and I and Gunn z for Stephenson 2. We derive a relatively old age of ~ 700 Myr for Pismis 23, with a reddening value of E(B-V) = 1.73 and a distance d_sun~ 2.6 kpc from the Sun. Stephenson 2 has a clump of red supergiants, indicating a young age of about 20 Myr, somewhat younger and more distant (d_sun~ 6 kpc) than recently reported in the literature. The age estimate for such a young object is crucial for the distance estimate. The high reddening of these two clusters relative to predictions from the diffuse interstellar medium at their distances is due to discrete intervening clouds. Observations collected at the European Southern Observatory - ESO, Chile. Tables 2 and 3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/390/931