Abstract
A preliminary analysis, concerning the site-testing compaign for an astrophysical station undertaken by the National Astronomical Observatory, is made on the basis of visual observations of night-time cloudiness made at four sites in the colombian Andes. Comparison with an independent study based on satellite images is made. Results show a minimum of 130 clear nights and a maximum of 250 useful nights per year at the site named Otun in the Central cordillera.
