We present an optical UBVRI photometric analysis of the poorly studied open star cluster IC 2156 using Sloan Digital Sky Survey data in order to estimate its astrophysical properties. We compare these with results from our previous studies that relied on the 2MASS JHK near-infrared photometry. The stellar density distributions and color-magnitude diagrams of the cluster are used to determine its geometrical structure, real radius, core and tidal radii, and its distance from the Sun, the Galactic plane, and the Galactic center. We also estimate, the age, color excesses, reddening-free distance modulus, membership, total mass, luminosity function, mass function, and relaxation time of the cluster.

Abstract
1. INTRODUCTION
2. DATA EXTRACTION
3. DATA ANALYSIS
    3.1. Cluster’s Radial Density Profile
    3.2. Photometry
    3.3. Luminosity Function
    3.4. Mass Function and Total Mass
    3.5. Dynamical State and Relaxation Time
4. CONCLUSION
REFERENCES

• Y. H. M. Hendy(National Research Institute of Astronomy and Geophysics)
• A. L. Tadross(National Research Institute of Astronomy and Geophysics) Corresponding author